Nonconformism has never been as fashionable as Anglicanism, nor so well- funded, and for doctrinal reasons its places of worship tend to be plain; "preaching-boxes" is the term often applied. But it was certainly popular and bewilderingly diverse. England has as many non-Anglican as Anglican churches - about 17,000 of them - but who can now tell the difference between Methodists and Independent Methodists, Baptists and Congregationalists, Unitarians and United Reformed?
All over England, in cities, on moorland, in old factory towns, their separate heaps of brick and stone stand as evidence of once-passionate debate and schism and clique, as well as to self-improvement and belief in God. Sometimes they have been converted to Indian restaurants, nightclubs, flats, second-hand furniture warehouses. Sometimes they stand open to the rain and wind. A surprising number, given the state of British Christianity, still draw clusters of people on a Sunday to listen to sermons and sing hymns.
In north London, I live quite close to a chapel. The Union Chapel (Congregationalist) stands at the northern end of Upper Street in Islington. Upper Street is very familiar to me. Over almost 30 years I have watched it change from a working-class high street to one of the chief parade grounds of London's young well-to-do, lined with bars, restaurants, estate agents and, in the Almeida, the most fashionable theatre in London. But of the Union Chapel, which after the town hall may well be the street's largest building, I knew nothing.
I noticed its clock. I noticed that it was a Victorian building set in the middle of a Georgian terrace. I wondered who, if anyone, went there and if anyone had ever answered the usual poster invitations to come inside and get to know Christ a little better. I was mildly surprised that it had not been demolished.
On Wednesday, my ignorance was corrected when the Union Chapel's minister, the Rev Janet Wootton, was good enough to show me the inside. Nothing had prepared me (I should have read Pevsner) for the sheer size and spectacle of it. The Union Chapel has polished oak pews that once held 3,000 people, galleries, stained glass, decorative tiles, marble, a great organ originally powered by water (which went on its course to flush the church lavatories).
According to Pevsner (later consulted) the style is 13th- century French Gothic, with a central plan inspired by the church of Santa Fosca in Torcello, on the Venetian lagoon. But that is just the chapel itself. At the rear of the main building lies a jumble of corridors and handsome halls built for Sunday School tuition and enlightened public meetings.
Congregationalism must have seemed a mighty and unquenchable movement when the chapel was opened in 1877. And now? Christian churchgoers account for 2 per cent of London's population. Mrs Wootton preaches to a congregation of 30.
She took me up into the pulpit, which she never now uses (too authoritarian to be modern), and explained the theological reasoning behind the church's design. How the pews arranged on three sides had no hierarchy - every worshipper could see and hear equally well. How the windows had no sills - and therefore no room for graven images. How the organ was screened - so as not to tempt the faithful into the worship of musical instruments.
She pointed to the ceiling, more than a hundred feet up, and said that behind the cupola lay an Archimedes screw, a great propeller to expel the foul air that would gather from a 2,000-strong congregation. Today, the problem is not ventilation but heat.
The Union Chapel was nearly demolished in 1980. Its survival owes a lot to the faith of Mrs Wootton and her congregation, but also to secular influence. The chapel is now listed by English Heritage as Grade II*, and the signage inside it is not always biblical instruction. As well as Sure and Steadfast, there is also No smoking and This way to the bar.
Thanks to an associated charity, The Union Chapel Project, all kinds of non-Christian events happen here. Rock concerts, readings, theatre rehearsals, Seamus Heaney, Eddie Izzard, Simon Rattle. The egalitarian beliefs of Congregationalism have given it perfect acoustics. Last year Rattle said after his concert: "I'm kicking myself that I've not been performing there for years." And, oddly for teetotal nonconformism, the church deeds do not proscribe the sale of alcohol. Mrs Wootton has done the research.
A great deal of money still needs to be raised, about pounds 3m for repairs to the fabric alone. The new plan is to make it "a theatre for the human voice" and focus on lectures, debates and choral concerts. Nonconformism is rich in the traditions of dissent and hymns (perhaps its greatest, and wrongly ignored, contribution to British culture). The Union Chapel would be a glorious and appropriate place to hear both.
Out in the traffic of Upper Street again, I felt the slight sadness of the non-believer. The Union Chapel does good work; its halls take in and feed the homeless, children with learning difficulties attend classes there. A shame, then, that one cannot share the spiritual motive of it, believe the story.
In a street and a world consumed by market forces - "renovated family semi-det house with 100ft gdn, en-suite bathroom to the master bed, pounds 595,000" - the Union Chapel is a refreshing and necessary thing. It was good, at last, to have discovered it.
LATE LAST year I wrote in this column about the wartime documentary films of Humphrey Jennings; about their brilliance as propaganda (because they were so reticently patriotic) and about the poetic lessons they could teach any contemporary British politician who was struggling to evoke a new British identity.
William Hague obviously did not read this, but then he is a busy little leader. His speech last week on Britishness, by which he may have meant Englishness, was the most terrifying encounter with folksiness since I last heard the late broadcaster Wilfred Pickles. You could see what the Tory leader was trying to do. Out with John Major's Fifties nostalgia and Baroness Thatcher's Churchilliana; in with something bang up to date. Consequently, we got the British as a "brassy" people who liked soap operas and a good laugh, and also (naturally) nourished a sense of fair play. It is not entirely inaccurate, but it would also fit Brazil or indeed any entrepreneurial nation with more than one television channel.
Also, it might double the emigration figures. He and the Chancellor, Gordon Brown (to whom Tony Blair seems to have dished out the "British question" job in the Cabinet), will have to try harder if they are to persevere as national- inspirers. Here is some advice, which came in a letter to me this month from Mary-Lou Jennings, the director's daughter.
She writes: "I was interested in your last point: the present need for some cunning, concrete poetry (if ideas of Britishness are to be revived). My father's work in film was, I believe, a mission based on his belief in the duty of a poet. In 1938 he did a series of broadcasts on poetry and the public, and in the one on poetry and national life he quoted Apollinaire whom, he said, believed that poets should stand with their backs to the future and face the past `because it was in the past that he could discover who he was and how he had come to be him'.
"My father added, `That idea of extracting an idea of what I am from the past is a thing that a poet does for himself, and especially it is a thing that he can do for the community; I mean, he can try and tell them who they are... [and talk about] the figures, the monuments, the achievements, the defeats, or whatever it may be that have made the community what it is.' That was what his films, like Listen to Britain, were about."
Politicians are not poets, of course, and you could argue that the past for too long has been a crippling national disease. But politicians who have tried to abolish it - Pol Pot, Stalin - failed among their many other sins to understand human and civic need.
Finally, a note on Jennings. He was probably the finest, most inventive documentary film-maker Britain has produced. He died young, aged 42, when he fell from a rock while he was filming in Greece. His daughter writes that she is beginning to think him "almost forgotten except among film buffs". She also says that he has no memorial of any kind. Even his grave in Athens has been destroyed.
Next year will be the fiftieth anniversary of his death. He deserves to be remembered in some permanent form - a plaque, a bust, an award, a scholarship. I would be happy to pass on letters to Mary-Lou Jennings with suggestions about where and how.