Italian priests were once a common sight in what is now Sai Kung Country Park, tramping between Hakka villages, ministering to the spiritual needs of an enthusiastic flock. Few traces remain of the missionaries, however, except for a handful of small churches, some abandoned, concealed in the farthest reaches of the countryside.

For more than a century, devout young men from the Seminary of Foreign Missions of Milan (now the Pontifical Institute for Foreign Missions) walked for mile upon mile along country paths to administer mass, or conduct a wedding or funeral.

It all started 150 years ago, on Pentecost Sunday 1866, when the first residents of the area were baptised by Father Gaetano Origo in Sai Kung, when what is now the town was a small, remote village on the southern periphery of the Qing empire. The missionaries set up a school and church (which was in use until 1959) in the village, near the Tin Hau Temple, as a base from which to access the small Hakka settlements dotted over the southern part of the Sai Kung Peninsula. To reach Sai Kung in the first place, they would have had to either take a five-hour junk ride from Hong Kong Island or hike across the mountains from Kowloon.

The Catholic history of Sai Kung was revisited last month, at the 135th anniversary celebration of the Immaculate Heart of Mary Chapel, a white-washed stone building located on a gentle rise on the outskirts of the isolated village of Pak Sha O. A special mass was read by Cardinal Joseph Zen Ze-kiun and the congregation spilled out of the little church - the fifth oldest of 11 that can still be found in the area - onto the grounds outside, to sing hymns in the cold.

The congregation was not made up of local Hakka villagers, though, because the original inhabitants all left decades ago, to seek a better standard of living in Sai Kung town, Tai Po or, more commonly, Britain. The village is now populated by a handful of expatriates seeking a tranquil lifestyle deep in the countryside.

"IT IS A VERY SPECIAL day; a long story of our missionary work," says Zen, at the event. "There is some sadness that none of the original villagers are here today but it is natural; the seed is sown and it disperses."

The congregation on this day consists largely of uniformed scouts and guides from the Catholic Scout Guild, who are responsible for the maintenance and upkeep of the building, along with the nearby churches hidden in Pak Tam Chung and Wong Mo Ying, where the Hong Kong Independent Battalion of the Guangdong People's Anti-Japanese Guerrilla Force was formed in February 1942.

"Frankly, it's very difficult to maintain this church," says Anthony Yeung Kam-chuen, secretary of the scout group. "We all live in the urban areas and there is no vehicular access here."

Pak Sha O is about 1km from the nearest road, along a path that passes through farmland and then beside a boulder-strewn stream.

Yeung's group was started in Hong Kong in the 1950s. It has about 100 members, ranging in age from six to 26, and they are allowed to use the church as a camping and adventure base in return for maintaining it.

Besides the three looked after by the scouts, the eight other churches dotted across the Sai Kung peninsula stand in various states of repair. Those in Tai Long Wan and Chek Keng are both still used occasionally for services, that on the island of Yim Tin Tsai is a Unesco-accredited tourist hot spot and the one in Long Ke Wan is little more than a pile of rubble.

Among the attendant priests at the mass at Pak Sha O is Father Sergio Ticozzi, one of the last in a line of holy men who served the needs of the Catholic villages until the 1980s, when almost all of the Hakka residents had left. Ticozzi is an authority on the history of the Catholic Church in China and is keen to point out that the church now being used in Pak Sha O is not the original building.

"The first chapel was built in 1880 but not on this site; it was over there," he says, pointing down the hill, through trees, back towards the village. Ticozzi celebrated mass for the villagers between 1971 and 73, when the "new" church, which had been opened in 1916, had no roof and the Pak Sha O population was already in decline.

"By the end of the 1970s, the village was more or less abandoned and the church was of no use," he says, explaining that that was when scouts approached the church authorities to ask if they could use the building.

THE ROMAN Catholic Church has been an integral part of the spiritual life of Hong Kong since the earliest days of the colonial era. Priests arrived from Macau in April 1841 and were granted land in Wan Chai on which to build a church. Primarily, they were required to tend to the spiritual needs of the young Irish Catholic soldiers employed by the British Army, many of whom were dying from malaria and other tropical diseases.

From the start, though, the Catholic clergy had misgivings about the religious potential of colonial Hong Kong and were keen to look north, to the mainland, as a target for proselytising.

More than 200 missionaries from the Milan institute have been sent to Hong Kong in the past century and a half, the first having been Father Paolo Reina, who arrived on orders from the Holy See in Rome on April 10, 1858. He was quick to gauge the religious potential of Hong Kong.

"With the exception of the soldiers there are very few English Catholics, no more than 20 … the other Englishmen respect us but they don't like to listen to anything about religion. Everybody is here to make money and then return to Europe," wrote Reina, in a letter dated March 9, 1859.

So as soon as the British acquired the Kowloon peninsula, in 1860, the Catholic Church set up a temporary chapel inside the military encampment and the pioneering Milanese missionaries started heading for the hills on foot.

"In those days, the Europeans dismissed Sai Kung as a dangerous pirate area and would never think of going," says Ticozzi, naming the first missionaries who ventured into the unknown as Father Giuseppe Burghignoli, originally based at the Kowloon military camp; Father Simeon Volonteri, a popular priest and keen cartographer known to the locals as Padre Ho; and Father Andrew Leong Chi-hing, a Chinese priest who attended the seminary in Hong Kong in 1850 with his uncle and was one of the first to be ordained here. This determined group of men assisted by a small team of catechists (lay teachers fluent in local dialects) set up modest mission stations in Wun Yiu (in Tai Po) and Ting Kok, on the northern shore of the Tolo channel.

"Our missionaries lived in China, they opened schools, then opened a chapel and later taught the catechism. Eventually this would lead to baptisms. It was a very different tactic to the Protestants," says Ticozzi, who explains that in 1864, Origo joined them in Ting Kok, and then became, in 1865, the first priest to take up residence in Sai Kung.

"They travelled on foot a great deal," says Ticozzi, and so extensive was their venturing that, in 1866, Volonteri produced a map of what was called San On district. The map was so detailed, it was printed in Germany and used by the British authorities as a primary geographical reference until after their lease of the New Territories, in 1898.

On Volonteri's map, the mission stations at Tai Po, Sai Kung and Ting Kok are clearly marked and there are accurate details of the eastern side of what is now the New Territories and Shenzhen. There is less detail on the western side and Lantau island is almost blank. Scholars believe the imbalance in the mapping was simply because the Hakka people, who proved receptive to the overtures of the small band of priests, were predominantly found in the hills of the east.

The Hakka (meaning "outsiders" or "foreigners", in Cantonese) had migrated south from the 14th century to set up farms, kilns and potteries in the remote hillsides not already occupied by the Cantonese-speaking Punti.

However, "the Hakka villages of Sai Kung were willing to accept Catholicism only when the people found the missionaries helpful, either in education or in social connection", says Father Louis Ha Keloon, a leading scholar at the Centre for Catholic Studies at Chinese University. "So, usually, the Hakka people needed some kind of connection, like a friend or a relative familiar with missionaries, before they would accept them."

Another theory to explain why these communities so willingly abandoned their own deities and customs is that the Hakka were transient and adaptable by nature.

"I think one of the contributory factors in those villages accepting Catholicism so readily was their need for a feeling of support in such isolation," says Ticozzi.

The young celibate priests immersed themselves in local lifestyles, and it was a tough life.

"They were often living alone, trying to learn local dialects, struggling with the hot and humid weather and often sick due to insufficient food intake," writes Gianni Criveller, in his book From Milan to Hong Kong.

Many lost their lives prematurely due to exhaustion, disease or accident. Origo died at the age of 33, just two years after he built the school and baptised the first locals in Sai Kung.

"Even in my day it was common to stay [for a night or two] with a local family in Pak Sha O and eat only rice with some salted fish and vegetables," says Ticozzi, remembering that it would often take more than two hours to walk from village to village. On one occasion, he says, he was unable to be collected by boat due to an impending typhoon so had to walk for eight hours to reach Sai Kung town.

"The food and conditions were far from ideal but I never minded it," he says.

After the baptisms in 1866 there was great enthusiasm from one clan of Hakka settlers in particular. The entire community of Yim Tin Tsai, a small island a 15-minute boat ride from Sai Kung town, had embraced Catholicism by 1875; the resident Chans were described by the church as being "converted and very fervent", according to Criveller.

When visiting Yim Tin Tsai, the head of mission in Hong Kong, Father Timolean Raimondi, who was not known for needless eulogising, thought he was experiencing an idyllic taste of his native Italy on the edge of China.

"Everything is done here according to the Catholic spirit. The island is entirely Catholic; processions and feasts are celebrated. Their way of living reminds me of our rural Catholic [Italian] villages where faith and simplicity still reign," wrote Raimondi, in 1874.

This anomalous taste of Italy is now a Unesco-award-winning cultural heritage site and its St Joseph's Chapel, built in 1890, has been lovingly restored .

Religious fervour was also manifest in the Hakka settlements of Tai Long and Chek Keng, the churches of which had both been built in 1867, and the Catholic faith flourished for more than a century in many isolated villages, the last church being erected in 1953, in Sai Wan.

A colourful vignette from those early days is contained in the account of a journey to Sai Kung undertaken by a retired Austrian ambassador, Count Joseph Huebner, written in 1870 or 1871.

"In each Christian village there is a small chapel with or without a cross according to the attitude of the population; beside it a miserable tiny room serves as residence for the priest during his frequent visits," wrote Huebner, whose party was to meet a young priest called Father Louis Piazzoli, who would go on to be ordained bishop of Hong Kong on May 19, 1895 and eventually die in the city.

"The tropical sun, the fatigues and worries of the apostolic life have not yet tarnished his nice and courageous face or the freshness of his youth," wrote Huebner.

THE LAST MEMBER OF the Chan clan to leave Yim Tin Tsai did so in 1998 and ferry services ceased. At their peak, from the 1930s to 50s, some 50 Chan households, or about 1,200 people, had lived on the island.

As families emigrated or moved to other parts of Hong Kong, Yim Tin Tsai and the other Hakka villages that once welcomed the priests from Milan began to fall into disrepair, along with their chapels and churches.

As they have done throughout their history, the Hakka have moved on, to seek a more prosperous place in which to live. Almost all that is left behind of their Catholic lives in the Sai Kung Peninsula are the little churches, the dilapidated village houses and the ghosts of the 19th-century Italian priests who first brought the faith to them.