The stillness of the pigs lingers in my mind. Prostrate, they were in adjacent stalls, snorting sporadically as if disturbed from pleasing dreams, snuffling, belching, deftly manoeuvring vast pink and black and white bulks to get the most exposure possible to the sun. Two enormous, oblivious Rotherhithe pigs, safe from American hog camps and Gloucester Old Spot sausages. Among global piggery, surely the most blessed of their kind.
Cycling the Thames Path on the south side of the river to the Thames Barrier was my friend Polly's idea. For me it was weekday work avoidance and I felt shifty about it. Polly arrived at Tate Modern from Clapham, me from Kentish Town. I was 20 minutes late. She raised an eyebrow.
My London, day by day, is work routes, pubs, pictures, bus stops, and when London-dwellers emerge from unfamiliar Tube stations we step into fragments of a jigsaw, not a narrative thread. Cars don't do it for me either. They do not place me inside this city of eight million; they provide either freeze-frame traffic jam or speed and blurred backdrop. Feet are fine, but slow, and I miss the sweep of the metropolis. Bicycles - crawling painfully up shallow gradients, cheating on no-cycling paths, spinning down towards the river - are what keep me part of the city. And the Thames Path follows water. It would be easy, I reckoned.
We stare at Tate Modern: Duchamp, Man Ray, Picabia, it proclaims. In 1947, national and local uproar accompanied the start of building on the site of Giles Gilbert Scott's Bankside power station. It would be an eyesore, critics said, an insult to St Paul's from Labour's planners, to add to the injury of the Luftwaffe-blitzed landscape, Dada as destruction. The first I saw of the area was childhood glimpses in Charles Crichton's Hue and Cry, created, like that future Tate Modern, in 1947. The Ealing film was wonderful, I thought - voids in the landscape of the mighty city, chases across wide open space. I remember two decades later, in the late 1970s, a winter night picking my way in the darkness - cycling, of course - along the then inaccessible river, hearing the hum of the generators and anticipating the destruction of Bankside.
In 2008, uproar, critics, the threat of destruction are long gone. There are no voids, in the 21st century; there is a multitude instead. We snake away from Tate Modern and its crowd. I still have a residual Seventies guilt about the metropolis and tourists, left over from lousy licensing hours, decay, piss, pissing rain, dog-ends and the leftover lie of Swinging London. In those days I felt I should go up to vacationers from Stuttgart and LA and apologise. "Look," I would say, "I'm sorry, it will improve. Later." Now it has. But the multitude at Millennium Bridge, they are just that, while we, I tell myself, are surely voyagers.
Under Southwark, London and Tower bridges we go, past HMS Belfast and the replica Golden Hind and on to Shad Thames, a Conranian village of Pont de la Tours where Stepford fishwives rub shoulders with Pizza Express sellers and rogan josh spice traders. Beyond St Saviour's Dock, everything changes. By Bermondsey the tourists and the City workers have gone. We pause by the pub at Cherry Garden Pier - where Samuel Pepys bought fruit from local orchards - and contemplate green space and ancient stonework. Polly asks the sole figure in the landscape, a man outside the pub, about it. He pauses. "Some old abbey," he suggests. The Reformation just won't go away. But he is wrong: a small notice identifies it as the 1350 site of Edward III's manor house.
In front of Edward's manor is Alfred Salter. At the end of the 19th century this doctor pioneered a local health service for the poor, and then saw his beloved eight-year-old daughter, Joyce, die of scarlet fever in 1910. Now a bench supports Diane Gorvin's warm sculpture of the man, contemplating the family cat, and poor Joyce, leaning against the embankment. I picked up on Salter a quarter of a century ago, during the Bermondsey by-election where old Labour died. Salter was used then as a club in the brawl between the Labour candidate Peter Tatchell, the villainous former MP Bob Mellish and the eventual winner, the Liberal Simon Hughes. It was left, farcically, to Michael Heseltine's London Docklands Development Corporation, in between watching the old place and old ideologies fall down, to fund Salter's monument.
My pigs are at the Surrey Docks City Farm, along with sheep, lambs, goats, kids, a couple of noisy cows, hens, a calf with angelic eyes, a black and white cat in a tree, and visiting families, some with pinched faces from 19th-century images of the London poor. Our Mutual Friend describes "that district of the flat country tending to the Thames, where Kent and Surrey meet, and where the railways still bestride the market gardens that will soon die under them". It looked, Dickens went on, "like a toy neighbourhood taken in blocks out of a box by a child of particularly incoherent mind". In those days the farm was a shipyard. Now it is surrounded by council blocks out of a box: Dickens's image persists.
Ridiculous, but I realise I imagine the Thames should be straight, or at least confirm north and south. Instead, of course, it is serpentine, and approaching Deptford and Greenwich through New Jersey badlands and newly constructed Disney World housing, I slip into a parallel universe. This is not a London I know, despite a drab interlude in Creek Road, and whitebait and chips in Greenwich. Canary Wharf, across the river, keeps moving north and south as the shoreline loops round the tip of the Isle of Dogs. I am on a spacecraft above - or at least alongside - Solaris, and its fantasia of silent skyscrapers, which, having been east and north, are now west.
Down grit paths, past scrubby offshore outcrops of nesting gulls, we slide into riverside alleyways beside ancient factories, painters perched in doorways, to the Millennium Dome. Then silence, space, sand shifters, mounds of rubble and cement-to-be, the guts of the city we left behind. Across the water is the glistening silver of the Thames Barrier. At a Mike Leigh-style cafeteria, we share a toasted teacake and an impromptu lecture from an amiable guide about the barrier's mechanical mysteries. It has taken us four hours to cover 15 miles, and it will take us a hundred minutes to get back. Only at London Bridge do I rejoin the city. The stillness has gone, in its place that astonishing multitude, that noise.