Reap where you have Soane

A man in a pink tailcoat opens the door to me. A quick probe in my bag, and I'm allowed into the room with all the gold. There it is, in great fat slabs like rich boys' toffee. A neat, round hole in the thick glass of a display case allows me to poke a forefinger in and touch the fat, buttery surface of pounds 70,000. My damp fingerprint fades reluctantly.

They are rather keen on gold at the Bank of England. In their museum they have Roman ingots, twined like barley-sugar twists, and Japanese bullion crafted into yin and yang bars - perhaps in an effort to balance more than the books. But I'm not here for the money. I've come to this great windowless monument to cash to satisfy my curiosity about its architect, Sir John Soane, who, from 1788, spent 45 years of his life on the Old Lady of Threadneedle Street. For him the building became "the pride and boast of my life".

He had other prides and boasts. There is his other great creation, the Dulwich picture gallery, and his two houses, the London home in Lincoln's Inn Fields, and the "country" villa, now subsumed into suburban Ealing. And there were other friends and connections, which I was to string together into a leisurely, Soane-themed amble half-way across London.

I wandered first through Soane's Bank Stock Office, a high, coolly elegant, oval-shaped hall with curving mahogany counters around the walls. It's not exactly as Soane had it built in the late 18th century. They knocked the lot down in the Twenties when the bank site was redeveloped, but had the decency to rebuild this room in exact accordance with the original plans.

There is a little more Soane to see in the other main room of the museum, the Thirties rotunda with, in the centre of the room, a display case of gold ingots piled up like profiteroles, or Ferrero Rocher chocolates.Around the room are draped female figures, caryatids, that help to support the domed, glazed roof. These are Soane originals, rescued from the demolition. They look as though they have a weight on their minds.

My second Soane spot is just four stops away on the Central Line, at Lincoln's Inn Fields, where he bought three adjacent houses in the tall, grey-brick terrace, and spent several decades creating a unique family home in which to house his remarkable collection of artefacts. It's a house of incredible richness, from the Pompeian red of the dining-room and library, to the sunshine yellow of the first-floor drawing-rooms. Soane created a magical illusion of space by placing mirrors behind exhibits, above bookcases and in recesses, and then he packed every nook and cranny with books, paintings and his vast collection of architectural fragments.

With the ingenious use of great, hinged panels, a room the size of a lift becomes a picture gallery in which the works of art are fanned as if on the pages of a giant book. And what works. Hogarth's The Rake's Progress is here - the tale of a young man's fall, from inheritance to madhouse, in eight canvases. In another tiny room are no fewer than three Canalettos.

This wasn't always a happy house. After his wife died prematurely Soane described it as "the Mansion of woe". He had hoped to fund a dynasty of architects, but neither of his sons - George and John - was interested. The dissolute George, indeed, ridiculed his father's architecture in two spiteful newspaper articles. Soane believed these were the "death blows" that killed his wife. The sons scowl from a portrait in the first-floor drawing-room, looking not unlike the Rake in the series of paintings downstairs.

My Soane-inspired route west took me close to Hogarth's country house, and I got off the Tube at Turnham Green to make a detour. If you have ever driven into London along the A4, and negotiated that landmark of automotive misery, the Hogarth Roundabout, you will have passed the house. When Hogarth bought it in 1749, it was to provide a place of retreat from London for his last 15 summers. Today, despite the fact that four lanes of traffic blare past its door, a high wall ensures that the garden, dominated by a 400-year-old mulberry tree, is still an oasis of calm.

Once, Soane's own country house was just a few fields away. Today it is a grind out through the suburbs. Soane bought Pitshanger Manor in 1800 and turned into his vision of a Regency villa, enhancing its yellow brick facade with four towering columns topped by caryatids, rather like the ones holding up the roof of the Bank of England. Except that, here, they had nothing but sky above them.

Pitshanger Manor has had its ups and downs. The grounds are now Walpole Park, and until the Eighties the house was the town library. But half a dozen rooms have been beautifully recreated, often with reference to watercolours showing original furnishings dating from 1802.

The other imposing thing about the place is the arched gateway. I'd seen it dozens of times, long before I'd heard about John Soane. And the reason for that is a little further down the green, in a Thirties building that bears the name Ealing Studios. This was home not just to the Ealing Comedies of the Thirties, Forties and Fifties, but also to much of the BBC's drama and comedy, including Steptoe and Son and Monty Python. Indeed, it still is. And, down the decades, if ever a director has wanted an imposing gateway to film a Rolls Royce purring through, they have popped next door, to this place.

The studios are only infrequently open to the public, but across the green is a pub, the Red Lion, which has always been the local for cast and crew. I finished my journey here, casting an eye over the photographs on the walls. There was Jack Hawkins, looking terribly British in naval uniform, Gina Bellman pouting in Dennis Potter's Blackeyes, and old man Steptoe, Wilfrid Brambell, leering away. And I noticed that he had a look in his eye rather like that of the Rake, and of Soane's dissolute son. What a trio. As George probably never said, but as Harold Steptoe might have: "Fah-vah, do try to behave properly."

Bank of England Museum, Threadneedle Street, open Mon-Fri 10am-5pm, adm free. Sir John Soane's Museum, 13 Lincoln's Inn Fields, open Tue-Sat 10am-5pm; first Tuesday each month, 6pm-9pm, adm free. Hogarth's House, Great West Road, open Tues-Fri, 1pm-5pm, Sat and Sun 1-6pm. adm free. Pitshanger Manor, Mattock Lane, Ealing, open Tues-Sat 10am-5pm, adm free.