When I first told my two teenagers that our next holiday assignment was to cruise the Canal du Midi in the south of France, and that we would be the sole crew of the boat, they shrieked.

“Mum, we’ve never been left in charge of a boat, this is madness,” said Elen, 19. “We’ll drown,” said Shaz, two years younger than his sister.

Six weeks later and, with Kevin, a family friend, roped in for assistance, we were surveying our new home for the next seven nights. Slightly bleary-eyed, having caught an early morning Ryanair flight from Stansted to Montpellier airport, followed by a 90-minute taxi ride to our first base, Port Cassafières at Portiragnes, we picked out our white cruise boat, bobbing peacefully among a flotilla of similar vessels on the canal.

Our mission: to take the boat up the canal, heading east and mooring wherever we pleased along the way as long as we docked the following Sunday at Saint-Gilles — a journey of about 65 miles, which meant about three hours cruising a day. Since the canal hugged the coast for part of the way, my aim was to treat the boat as a floating seaside cottage, stopping off at as many of the beaches on the Riviera as we had time to enjoy.

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I had my sights set on bike rides to secluded beaches, afternoons swimming in the Med and lazing on the sand, and evenings scoffing French cuisine in village restaurants. I’d even packed Kate Mosse’s novel Labyrinth, a fictional account of the bloody Fourth Crusade, launched against the Cathars in southwest France in the 13th century, since we were going to be passing close to some of the sites of slaughter, including the town of Carcassonne.

First came our lesson on how to sail the boat, from a sun-beaten Englishman, John Atkins, who made it look so easy as he glided us smoothly away from our moorings, up the canal and then back again. “Don’t worry about bumping it. The only thing you have to worry about are the locks,” he advised. “Choose one person as captain, to steer the boat, then give the rest of the crew a job to do.”

“Captain Kev,” the kids chorused, and that was that settled. Shaz was in charge of lifting our bikes on and off the boat and tying it up when we moored. Elen was the map-reader and translator. I settled for chief cook, bottle washer and tidier-up of our tiny cabins.

As the elected captain reluctantly took the wheel and started the engine, Atkins added: “This is two holidays in one. For the youngsters there’s the sun, the sea, the beaches all along the way. But then there’s the canal, too, which is a historical monument, and all the villages you will pass, a glimpse of French France. A canal boat is not a means of transport — you can’t go faster then 5mph — it’s a way of life. So take it easy.”

The story behind the Canal du Midi is certainly a romantic one. It was a 17th-century visionary, Pierre-Paul Riquet, a businessman from Languedoc, who dreamt of linking the Garonne (and hence the Atlantic) to the Mediterranean, via a canal 150 miles long.

The aim of the shortcut was to avoid a long sea voyage around Spain and the ferocious Barbary pirates one might encounter en route. As the project advanced, overcoming countless seemingly insuperable engineering obstacles, it slowly bankrupted its creator, who, sadly, did not live to see its completion.

These days it’s rare to see commercial vessels on the canal (we passed just a couple of massive ironclad barges), but it’s one of the most popular tourist waterways in Europe. “We should have brought a little Union Jack,” said Elen as we spied other tourist canal boats with national flags fluttering from their decks.

Day One and we moored near the village of Vias, tying our boat up to the bank using the ropes and metal stakes we had on board. A quick cycle ride to our first French beach stop, Vias Plage, a plunge into the sea and an hour baking on the sand, then back to the boat and our first challenge, navigating one of the canal’s 90-plus locks. Somehow we fumbled through, to cheers from the handful of locals who had gathered to laugh at our efforts, and then it was up to the town of Agde and our first round of moules frites washed down with red wine.

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