But fast forward 45 years and the impossible project is finally moving towards an astonishing, if somewhat ramshackle, conclusion. Its inimitable architect and builder has gone from loco - nuts - to a more respectful Don Justo.

'As they have seen the cathedral grow they have realised that I am not mad,' he informed a Spanish newspaper last week through his trademark toothless grin.

For three decades the wiry loner, now 81, has been a novelty news item in the Spanish media, and has been making headlines again after an ironmonger donated and delivered the sprawling building's main doors. A French artist has offered to decorate the interior.

The scale of the undertaking stuns the bus loads of tourists who make pilgrimages to the site in Mejorada del Campo, 22km from Madrid. The main building is 50 metres long, with the heavy metal frame of the dome reaching 40 metres into the air. Beneath the uneven floor is a huge crypt. There are also, at various stages of construction, minor chapels, cloisters, priests' lodgings and a library. In total the structure occupies 8,000 square metres.

But question marks remain over the quality of his workmanship. 'I am not an architect or a bricklayer, nor do I have any training in building,' Gallego candidly admitted to one reporter. Evidence of his unorthodox approach, allied to wild improvisation borne from lack of funds, is everywhere.

Gallego's cathedral is a monument to recycling, built largely from materials found in rubbish dumps, scrap yards and abandoned building sites. Walls and staircases are made from broken bricks, held together by cement. Door and window arches have been moulded with old car tyres or wheels, and columns with rusting petrol drums. Since he started, aged 36, Gallego has worked there 10 hours a day, six days a week, through baking Spanish summers and the deep freezes of winter. After roughly 14,000 days of hard labour, he still has no time for holidays.

Assistance has been rare. When the time came to raise the dome's heavy steel girders into place he was unable to borrow a crane. Help from six nephews, and pulleys made from rope and bicycle wheels, proved an adequate alternative.

His dream was born almost half a century ago when his ambitions to live a life of solitude as a monk were dashed. While living at a monastery he contracted tuberculosis and was banished by an abbot who feared an epidemic.

Gallego can't recall why he opted for such a strenuous Plan B, but his mother had wanted him to work for the church, and he decided building the cathedral was the best way to serve God. Funds were raised by selling and renting land on an olive grove he had inherited.

'I started building because I wanted to purify my soul,' he said recently. 'We sin all the time - I do every time I see a beautiful woman. Kings, lords and bishops, they can all build cathedrals. But here is just one simple believer doing it.'

Unlike other cathedral builders, Gallego has never produced any written plans or architectural drawings, which he considers a waste of time. Everything, he says, is in his head. It's for that reason he has never applied for a building licence that legally requires an architect's official stamp of approval.

For many years town authorities ridiculed Gallego, questioning the structural safety of his creation.

He has bequeathed the cathedral to the local bishopric, but Catholic authorities treated his donation with disdain. They already had a cathedral, and didn't need another one.

As the scale of Gallego's endeavour has become more apparent over the years, the once obsessive fool has become a symbol for the triumph of human spirit.

He recently starred in a TV advert for a popular soft drink as an example of how people can turn their dreams into reality.

The latest donations to his project come as political and religious authorities adopt a more conciliatory tone on what will happen to the cathedral when he dies. They are still not sure what to do, but tearing the building down seems off the agenda.

Just when, or if, Gallego concludes his dream is also open to debate. With the right help, he believes it could be finished before his 85th birthday.

But the man who lives with his sister in avowed poverty dismisses flattering comparisons with a more celebrated builder, the Catalan architect Antoni Gaudi, or other historical figures.

'They say I'm quixotic or mad,' he says.

'No doubt they'll nail me to the cross. But Quixote does not interest me. This is real.'