The African Queen which rules the waves

Sitting on the deck of the boat, with the sun about to set, we meander sedately downriver.

It is a Wind In The Willows experience but less rushed: Jerome K. Jerome without the sense of urgency.

On this stretch of the Thames, there are no roads, just farmland, an occasional walker on the towpath and a series of grand houses with lawns down to the water. Just one boat passes us.

Food for thought: Bonny and Andy Cowley

After a while, Andy Cowley, the skipper and owner of the African Queen, turns the boat around and we head back to its tree-fringed mooring at Mapledurham, near Reading.

Nothing much daunts Andy. When he bought the African Queen in 2004, he sailed it across the Irish Sea and has done battle with numerous officials to breathe life into his gloriously eccentric dream of owning a cruiser on the Thames.

But Alex Polizzi is another matter. She's the Hotel Inspector on channel Five and she's on board, along with a film crew, to see if Andy and his wife Bonny have taken up her advice. Alex, in her mid-30s, has a touch of the doughty Katharine Hepburn about her, ready to fight bad hotel-keeping on all fronts.

Alex's grandfather founded Trust House Forte. Rocco Forte, her uncle, runs hotels around the globe, from the Balmoral in Edinburgh to the Astoria in St Petersburg. Her mother Olga owns the acclaimed Hotel Tresanton in Cornwall and when she's not in front of the cameras Alex runs another of the family's hotels, the Endsleigh in Devon.

Critical eye: Hotel Inspector Alex Polizzi

All of which must make the dingy, badly run establishments that she takes on on TV hard to stomach. She's a hospitality surgeon, generally prescribing bleach, repainting and the virtue of keeping tidy accounts.

'It always amazes me when hoteliers and B&B owners don't keep account of the costs that mount up so easily, from laundry to croissants,' she says when she shows me around. 'If you're not aware of where your costs are going, then you are in trouble.'

Andy and Bonny Cowley are fully aware of their costs. From converting the boat into a hotel and finding the mooring, they've been huge, and last year they turned to the Hotel Inspector to see if Alex could stem the losses.

Andy, originally from the Isle of Wight, emigrated to South Africa as a boy. In his 50s, he and his wife returned to Britain and ran a hotel back on the Isle of Wight.

The African Queen came about through passion, irrationality and sheer persistence. After seeing an advert for the boat, the couple decided to start a floating B&B, with restaurant-quality food, plus cruises along the Thames.

With five double rooms, two singles and a suite (as well as the part that Andy and Bonny live in), the converted barge is spacious. It's more than 100ft long and there's also a large deck and sitting room, with a bar.

So, why did the African Queen need the Hotel Inspector? 'We've tweaked a few things - changed the blinds and brought in some cushions on the top deck but Bonny's food is wonderful - it's as clean as a pin and it's unique,' says Alex.

'Ultimately, I think its problem is that it just doesn't fit into the usual hotel box. It's a hotel and a restaurant and a cruise.'

Back at the mooring, Bonny produces, from a galley kitchen the size of a large cabinet, course after course of delicious food: rich stews with fruit and spices.

'It's Cape Malay cuisine,' says Andy, who is playing the host while David - deckhand and waiter, an expat South African - hands round the plates.

'It started when Malaysian prisoners arrived in South Africa in the 18th Century,' says Andy.

Scenic: A bridge over tranquil waters provides a picturesque view from the African Queen

We finish off with Dutch milk tart and I'm aware that the film crew are looking on enviously.

In the course of making this year's Hotel Inspector, not only did Alex sleep in lumpy beds, shudder at dirty bathrooms and wince at painful decor, so did the crew. Over the past six months, they have experienced some of the worst hospitality Britain has to offer.

After filming our dinner has been completed, Bonny brings out more food for them, which they leap on with enthusiasm. The African Queen, they say between mouthfuls, has had by far the best food of the current series.

My cabin is tiny but sweet. A couple would have to clamber over each other to get in but it's shipshape, with crisp white linen, bedside lights and high comfort levels, including electric blankets to supplement the central heating.

It's not the most soundproofed of rooms but I'm lulled to sleep by the gentle rocking of the boat and next morning a family of ducklings have taken to the water.