In fact, despite its urban setting, the boat had a way of encouraging flights of bucolic fantasy. When not kept awake by the resident rat gnawing through the bulkheads, I dreamt of chugging through a green and pleasant England along tree-framed canals. The dreams had a pre-war Edwardian glow — church spires and fluffy clouds and picnickers along the bank — that made waking to a view of Sheffield council flats a trifle dispiriting.

For the unwise, fantasies are merely actions delayed. And so I found myself captain for a week of a 58ft narrow boat called Joey, navigating the Oxford Canal. Gaily painted in red and green, Joey’s exterior was poignantly reminiscent of a gypsy caravan. Inside, things were more subdued, in a style that could only be described as caravan chic. Joey was fitted out with two double cabins, a loo with a bath and a shower, a saloon with a CD player and a television, and ample storage space for the mountain of unnecessary stuff that I had packed.

My crew consisted of three vaguely feral godchildren. There was the 14-year-old so deep into Harry Potter that you could have shoved burning matches under her toenails without her noticing; the eight-year-old fresh from a sailing course, who hadn’t got any further than knots, and the imperious five-year-old, a sort of pint-sized Captain Bligh.

Naively, I had set off thinking of myself as captain of our jolly ship. There would be games, laughs and larks on the canals. I would have quality time with my three charges that might make up for all those forgotten birthdays.

A harsher reality soon dawned. I wasn’t so much captain as hostage. None of the godchildren was old enough to take a turn at the helm. They became Joey’s officer class, largely idle and loudly superior, while I was demoted to common sailor, lashed to the wheel, a creature so insignificant that nobody bothered to relieve his watch. Free from adult interference, the juvenile officers lounged on the roof, made smoothies from raspberries and Dairy Milk chocolate bars, fished for frogs, fed my favourite biscuits to ducks, called friends in America on my mobile, lunched on cornflakes, poured lemonade over my iPod and generally dissed the godfather.

In spite of the presence of this alarming trio, the whole thing was eerily reminiscent of my Sheffield dreams.

Canals are a parallel universe. They exist in a time warp, in an England older than the motor car, older even than trains. Accompanied by ducks, who seemed to enjoy the biscuits even more than I did, we slipped through Rugby without a traffic light or a pedestrian crossing. Roads appeared only as picturesque bridges. Villages were enclosed by fields and sheep, rather than roundabouts and bypasses. Such are the illusions of canals. It was as if the modern world had melted away.

Our canal, the Oxford, was one of the earliest of the great industrial waterways. Built in the 1770s and 1780s, it was intended to carry coal from the Warwickshire pits to Banbury and Oxford, as well as providing a connection to the River Thames. Made partially redundant by newer and bigger canals, with shorter routes between the Midlands and London, the Oxford retains its rural character, particularly from Napton southwards, where it meanders as wilfully as a river.

At Hillmorton, we came to our first locks, a set of three. My crew had been thoroughly briefed about lock operation over breakfast — in a Blue Peter sort of way, using a cereal packet, a milk carton, a teaspoon and a cassette of Beethoven sonatas that they had destroyed the previous evening. They now jumped ashore and raced ahead along the canal paths with their lock keys, eager to put theory into practice. I moored behind another waiting boat and raced after them, arriving just in time to stop them pulling the plug on an elderly couple in their retirement barge.

Soon, it was “our turn”. The children took charge of the lock while I manoeuvred the boat. Captain Bligh ran back and forth issuing orders, while the Harry Potter fan and the Knot Expert laboured at the paddles. The gates opened and we drifted in. The paddles were lifted and we glided mysteriously upwards. The children were thrilled. “Awesome,” they chorused. For the moment, this simple mechanical piece of pre-Victorian engineering seemed to hold as much excitement as a computer game.

Locks are the social hub of the canals, the equivalent of the corner post office or the local pub. It’s common to help one another, opening gates and lifting paddles as you swap gossip and warnings about aggressive swans. From the helm, I could see my three charges chatting and laughing with the other boat owners while they waved me imperiously through the gates. After three locks, they had all the swagger of a lifetime on the canals.

“We told them you were on weekend release,” my godchildren laughed as they skipped aboard. “And that you had to be back in Belmarsh by sunset.”

We pottered southward through open rolling farmland. In the canalside pastures, sheep wandered across the ribbed ridges of medieval field systems. Astern, a windmill straddled Napton Hill. Ahead, farmsteads nestled beneath Priors Hardwick ridge. Beyond a field of yellow wheat, a train fled towards London.

The irony of the canals was that they were so quickly overtaken by the next new thing — the railways, faster, more flexible and more efficient. By the 1840s, they were already in slow decline. By the mid-20th century, many were in such disrepair that they were unnavigable. Their revival is due entirely to leisure use. British Waterways has overseen decades of restoration work. In the past 10 years alone, aided by lottery grants, as many miles of canal have been restored as were built in the great canal-digging decade of the 1790s.

South of Napton, the canal twisted and turned through north Oxfordshire towards Fenny Compton. On such a summery afternoon, the canal was a Wind in the Willows world of pastures and villages, of country lanes and manor houses. Dragonflies nosed among banks of rosebay willowherb and blackberries, swans paddled in willow shade, and swallows dived on the glassy surfaces ahead. At Banbury, the canal passes through the centre of the town, where it has become the focus of a new development of shops, cafes and a museum, as well as old Tooley’s Boathouse, where Tom Rolt’s boat was prepared in the 1930s. We moored for what I naively thought would be a bit of a stroll. But Banbury might have been Manhattan for all the excitement it generated among my crew. They hit the Castle Quay shopping centre like sailors on temporary shore leave. They had cookies at Millie’s, ice cream at Yogen Fruz and pizzas at Pizza Express, while I lugged supplies from Somerfield.

The excitement and the sugar rush seemed to leave them dazed. We chugged on through the late afternoon, with golden light raking across the pastures. Momentarily bored with the company of the others, the eight-year-old deigned to pay me a visit at my lonely post.

We chatted a bit, then he settled down to write postcards. The card to his parents consisted of one word — WICKED.