After the meal, I ask him how he celebrated his birthday. He came to work as usual, he says with a shrug. This is what he does, this is his life. “The life of the shokunin [a Japanese artisan] is like a sportsman,” nods his son, Yoshikazu.

Everyone knows the Japanese take sushi very seriously indeed, and with that in mind they have created an organisation to promote good sushi-making around the world. The Tokyo-based World Sushi Skills Institute (WSSI) is funded by the Japanese Ministry of Agriculture, Forestry and Fisheries to tackle such horrors as mushy supermarket sushi, “Asian” restaurants that serve Thai, Chinese and Japanese food from the same kitchen and, in particular, poor hygiene leading to the kind of food poisoning outbreaks that recently prompted the New York Hygiene department to insist sushi chefs wear plastic gloves (“Can’t make sushi with gloves!” one of the city’s leading sushi chefs barked when I asked him about this).

My first insight into the WSSI’s global quality-control strategy came when I was a judge at the British round of the competition, held at London’s Nobu restaurant in September.

Hirotoshi Ogawa, a short, straight-backed Japanese man wearing a white lab coat and brandishing a clipboard, is the WSSI’s chief examiner. He tells me to keep a special eye on whether contestants regularly rinse their hands in the bowl of vinegared water provided, essential for killing bacteria.

Nine professional sushi chefs (seven male, two female) are competing in London to reach the final in November in Tokyo. Some are from prominent London restaurants – Saka No Hana and Sushi Samba – oligarch canteens, essentially. Some are from less prominent spots, such as Sam Butler from the House of the Rising Sun in Shrewsbury, in the English West Midlands.

They face three challenges: the first is to make a plate of classic Edomae sushi in 10 minutes. This is the style that evolved in Tokyo in the 19th century, based on seafood caught in the city’s bay and nearby, and which, loosely speaking, is the nigiri/maki sushi we know best in the West. Only the members of the WSSI are deemed knowledgeable enough to judge this round. The second round, “original sushi”, requires the contestants to make 20 pieces in their own style in one hour; for the final round, they have to present a single piece of their signature nigiri for the judges to taste.

The 10-minute challenge begins: contestants must make seven nigiri and one maki roll. “In Japan, the chefs are perhaps not so creative, but they are much faster. There, we only give them two minutes,” Ogawa confides.

The round has a frantic feel. At one point, I try to lighten the mood by chatting to one of the contestants, Poppy Sherwood from Wabi in Horsham, south of London.“No talking to the contestants during the 10-minute round!” scolds Ogawa. All but one contestant fails this round.

We move on to the second round. This goes better. There is a wide range of nationalities competing, including Polish, Brazilian, and one man of Chinese background, who was born in Rome.

Diana Pinto Basto de Carvalho, chef at Gordon Ramsay’s Maze Grill Park Walk in London, produces sushi that is delicate and attractive, but she uses cream cheese and mango-chilli sauce, and I mark her down accordingly. Wojciech Popow from Yashin Sushi has assembled an alarming array of ingredients including chocolate, smoked salmon and Hibiki whisky jelly for his signature piece. Tai Po Wong, from London’s Sushi Samba, pulls out all the stops with foie gras and caviar, but his plate is a little too busy for the Japanese judges.

In this round, we are encouraged to talk to the contestants as they work, as interaction with diners over the traditional sushi counter is an important aspect of the job, which the judges are keen to stress is complex and difficult.

“Some people, they come to Japan for a three-week course and think they are a sushi chef,” chief examiner Ogawa says to me, shaking his head.

He has impeccable credentials for the job. After seven years training in Tokyo, the first five of which were mostly spent carrying out menial tasks, Ogawa worked for some years in Sydney, serving sushi to the likes of Nicole Kidman and Keaunu Reeves, and then ran his own restaurant in Tokyo.

The work of the World Sushi Skills Institute is not without controversy, he admits. In Japan, there is anxiety among some chefs about disseminating the secrets of great sushi to the outside world. Outside Japan, there has been resentment at what many see as their finger-wagging approach. “They are very strict about what they think is the right way to do things,” one of the contestants grumbled to me out of earshot of the Japanese judges. Some of the contestants in London have been working as chefs for over eight years, so it can’t have been easy being told everything they knew was wrong.

In the end, the judges agree that, against the odds, the whisky-chocolate-smoked-salmon nigiri made by Wojciech Popow is the best single piece in the London round – but he is not going to the final in Tokyo. A shell-shocked Xia Jia Tian from Rome, currently working at restaurant Kouzu, close to London’s Victoria railway station, is the winner.

Tian and I meet again in the last week of November, in the vast function room of a posh hotel in Tokyo. This time, I am judging alongside Yoshihiro Narisawa (multi-award-winning chef at his eponymous Tokyo restaurant ), and Ryu Hwan Tan of Michelin-starred Ryunique, in Seoul, plus the WSSI chefs. There are 14 finalists – all male. and there are TV crews from Japan, Turkey, Korea, France and elsewhere.

I shadow Narisawa and Ryu, and back in the judges’ room we are in agreement: the US and Norway were excellent, and I can see Tian has been practising hard, but Dae-Won Han from Korea just pips the Japanese chef. However, Han cut his finger at one point, incurring a penalty that drops him to seventh. Narisawa politely protests, but for a sushi chef to cut his finger in front of diners is unthinkable. The decision is upheld.

The winner is, perhaps inevitably, Japanese: 45-year-old Jun Jibiki of Tokyo’s Koma Sushi. “I felt so much pressure, being the Japanese entrant,” Jibiki tells me afterwards. “I really understand for the first time the creative possibilities with sushi.”

On stage at the award ceremony, Ogawa-san takes the microphone, and the exhausted contestants, still in their chefs’ whites, line up behind him in front a 200-strong crowd.

After a few words, much to everyone’s astonishment, this tireless taskmaster breaks down and begins to cry. Months of tension are released as he thanks the contestants and praises their efforts, tears streaming down his face.

Michael Booth is a British food writer who wrote the book Sushi and Beyond: What the Japanese Know About Cooking, which was adapted into a Japanese television anime series which began airing in April 2015.

The Guardian