There are no guests inside the church, just the minister, a translator from the tour company and an obtrusive team of three photographers who monopolise the whole event.
The groom, 28-year-old Takashi Kumagi, a television director in Sapporo, looks time and again to the bride, 31-year-old Izumi Kumagi, throughout the service.
They later admit they hardly understand a word of what is going on. After a short passage from Paul's gospels, 'so faith, hope, love abide. . .but the greatest of these is love, they repeat, in rather shaky English after the minister the words: 'I will, with the help of God.
They exchange rings, sign the register, and within 20 minutes the whole thing is over, bar the photographs. Izumi wipes away a tear as they reach the church doors.
Takashi says he decided to get married in England because he liked the country so much. This is his third visit. But cost was also a deciding factor. A formal wedding ceremony in Japan, which would involve inviting up to 500 work colleagues, would cost as much as pounds 15,000.
Instead the trip to London, including the wedding, set them back just pounds 5,000.
Neither he nor Izumi have any religious belief, so they are not worried about coming into a Christian church, he says. Nor are they bothered about the religious context of the service. 'It's just a ceremony, he says .
Izumi says she does not mind not having her friends there, as they already had a civil ceremony in Japan. She has thoroughly enjoyed the whole trip.
Next stop is a week on the Cote d'Azur before returning home.
British couples may choose to escape the horrors of a big family wedding by getting married in Barbados or some other exotic resort abroad, but among the Japanese, the latest fashion is for couples to have their wedding in London.
Japanese tourist companies are providing package tours to Britain which include a marriage blessing ceremony as part of the deal. The tour companies arrange a car, hire of a traditional white dress and veil for the bride, morning suit for the groom, photographers and, if the couple wants it, a video as well.
The American Church in Tottenham Court Road, just opposite Heal's, will perform the half-hour service for an all-in fee of pounds 425. This includes flowers for the bride, a buttonhole for the groom, and a bouquet on the altar, plus an organist to play the Wedding March.
The weddings take place on Tuesday and Thursday afternoons only, so as not to interfere with the rest of the church's work.
Some of the money raised goes to finance a soup kitchen for homeless people, run four mornings a week from the back of the church.
Couples cannot be married in England unless they have been resident for 15 days, so most have a registration ceremony in Japan beforehand, followed by the blessing in London. It is possible, though, to get married in Scotland, where the residency rules are less strict. Some couples pay nearly pounds 2,000 to be married in Edinburgh.
But to any observer, the London ceremony they take part in looks as much like a wedding as the real thing.
Overseas weddings are big business in Japan, with Australia and Hawaii the most popular destinations. But London is becoming increasingly popular as a destination. In the past year, the American Church has blessed more than 40 Japanese couples, compared with just a handful the year before. In fact, the numbers have grown so much it now employs a part-time assistant purely to organise the weddings. It made about pounds 17,000 from the ceremonies last year, more than enough to fund the soup kitchen, which costs about pounds 10,000 a year. The rest of the money goes into missionary work and overseas projects.
The American Church was originally a naval chapel for US servicemen during the war, but has since been incorporated as a church in its own right, registered in Delaware. It is inter-denominational, with a range of ministers from many backgrounds. Although it is Protestant in doctrine, affiliated to the United Reform Church, it even has Roman Catholics in its regular congregation.
'There were just one or two of these weddings when I started working here a few years ago, said Barbara Gardiner, the church secretary. 'But they started coming more often so we decided to increase the charge and make it more formal.
As part of the ceremony the couple receive 20 minutes' counselling with the minister beforehand when they are told what the ceremony involves. They also receive a Japanese translation of the English service; a certificate saying when and where the marriage blessing took place; and a pounds 25 leatherbound copy of the Good News Bible in Japanese.
The church has learnt to keep the service simple. Although some couples speak a little English, a lengthy service may be too complicated. For those who do not speak English at all, a translator can be arranged.
Most of the couples are not Christian. The official religion of Japan is Buddhism. Some Japanese are Shinto, a handful are Christian, but most are not religious at all.
The biggest attraction of the overseas weddings are financial rather than religious. By marrying overseas the couples save on the enormous cost of a wedding in their own country. Japanese etiquette requires them to invite all their work colleagues, which can mean 200 to 500 guests. A formal wedding might involve a religious or civil service followed by a huge reception afterwards.
It was a difficult decision for the church to become involved in the venture at first, admits Barbara Gardiner. 'There has been a fair amount of heart-searching over whether we should or should not do it. We wouldn't want to end up being another Japanese tourist spot.
But they have decided the ceremonies are part of the church's outreach work. Two weeks after the ceremony the couple are sent a letter with details of their nearest Christian church in Japan.
Although Ms Gardiner has no idea how many follow up the invitation, she has had Christmas cards from couples who married at the church, saying how happy they are.
The Rev John Hambrick, one of three ministers who performs the ceremony, argues that by giving the couple a copy of the Bible and translation of the service, they are offering the couple something which may be significant in later life.
'My hope is this service will be a catalyst that God can use to begin these couples becoming Christian, he said.
He sees nothing wrong in making money from the service. 'I don't personally make any money. Only the organist and the photographers get paid.
'Churches charge for all sorts of services. I don't think money is a bad thing, it is what you do with it.
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