Stephen Naysmith

The only rule is: Speak to the keeper of the lock. No sign of a lock keeper? Go looking for them. You don’t want to get on their wrong side. If that happens, you’re probably going to stay the wrong side of the lock, and that means you aren’t going anywhere.

“I was only up there,” says one gruff example, gesturing to the picturesque cottage above the lock. "Didn’t you see the car?"

A few minutes earlier he had boiled over as I asked if we could, “get up” through the chamber to continue our voyage towards Loch Oich.

It was Sunday, 5pm. We had been told the locks were open until 6pm. That seemed like useful information. It turns out this is not a rule.

So when we reached the lock at 2pm and found it unmanned, we assumed the keeper was at lunch, and we went for our own. We walked up to the nearby Thistle Cafe – a hotter, longer trek than we had envisaged.

By the time we returned it was nearly 5pm. But plenty of time, still, to navigate the lock. Unless you forgot the only rule: speak to the keeper.

“I thought you’d tied up for the night,” he fumed. I think we might have interrupted him watching the football.

Not all the keepers of the locks are ogres. But they can certainly be intimidating. Throwing a rope seems not so hard, until you’re doing it under the eye of an impatient and despairing lock-keeper as she looks down at you with a mixture of pity and infuriation.

Spotting a newbie family, rather ill-equipped to be piloting a 40ft cruiser towards the largest, deepest stretch of inland water in the British Isles, I can forgive the impatience. And if you do follow the One Rule, you can benefit. Another keeper gave us good advice about running ashore.

Meanwhile, the glow when they praise you for a perfect manoeuvre to position in the chamber alongside the wall of the Steps at Fort Augustus? Well, that is matched only by your ill-concealed schadenfreude as the swanky Swedes on the other side in their showy yacht, the one with the 18ft mast and the artfully arranged collection of herbs in little pots on the tiller, get a telling off for failing to control their vessel.

Our vessel was an Elegance, boasting three staterooms, three bathrooms, saloon and sundeck. That sentence, and the idea that the Skipper’s Guide to the Caledonian Canal might apply to me, were quite the novelty. But the skills needed to pilot a motor cruiser from Laggan Locks on the tautologically-challenged Loch Lochy, to the heart of Loch Ness are readily come by, it turns out.

They are provided, somewhat minimally it would be fair to say, in a half-hour briefing we received on collecting our vessel from West Highland Sailing on a sunny Friday afternoon. How to reverse, how to manoeuvre, how to tie the boat up, where to find the charts and that’s about it.

But the addition of an hour or two of practical self-tuition on the still waters of Lochy itself, followed by a gentle couple of hours steaming peacefully along the canal toward Loch Oich sees us all getting the hang of it, kids included.

Later, a misguided attempt to dock in the crowded marina at Urquhart Bay, near Drumnadrochit gives us a more realistic sense of our limitations. We remain grateful to denizens of the harbour, half of whom who mucked in, pulling on ropes, to help us rescue ourselves from an ‘arse-backwards’ predicament. The other half, it should be said, sat on their decks sipping Chardonnay and looking at us with ill-concealed disdain.

And make sure you check before trying to dock at Urquhart Castle. After a stressful few attempts to manoeuvre into a jetty clearly marked on our maps, we finally made it in... only to be bellowed at by a castle staff member and moved on. What a welcome.

If a weekend trip on the Caledonian Canal conjures up images of cramped narrowboats, and bleak towpaths, think again. Hiring a motor cruiser means comfortable cabins, a well-equipped galley, lounge with DVD player, as well as the option to steer from an internal cockpit, or from above, on the sundeck. The boats are much more spacious than you would expect with every comfort.

Tying up at night can be done at well equipped moorings in places like Loch Lochy and Fort Augustus, or in sturdy but blissfully remote stops between the locks – somewhere like Kytra Lock.

Prices vary for a week, to a long weekend. Guides urge you to take your time, but be warned, you’ll need to make progress if you want to get all the way to Loch Ness. We did, but had to talk our way past the sternest lock-keeper of all here.

He thought little of our chances of getting all the way down the steps at Fort Augustus and into the loch and still making it back in time to ascend the stair to give us a chance of returning to base by Monday morning. It takes an hour and a half to navigate the locks in each direction.

“You’ll waste three hours of your life", he says, "And Loch Ness isn’t all that.”

Not quite on message for Visit Scotland, then. But the One Rule mattered here more than ever. “Three hours pulling our boat up and down the steps is not a waste to us," I say. "It’s what we came for." I don’t mean Loch Ness, I mean the leisurely descent down the chain of chambers, pulling a giant boat from each to the next.

So he yields, with dire warnings about what happens if we make it back late for the the first ‘locking’ in the morning. We are rewarded with a dazzling, perilous (as Loch Ness is far, far more choppy than the canal which reaches it) sunset sail on Scotland’s most epic stretch of water.

No Nessie, not even a sighting of giant eels. The only monster here is the boat we can barely control, bucking so hard in the swell that a wine glass topples and smashes in the kitchen cupboard.

We made it back. And another phlegmatic gate keeper gives us a final vote of confidence. “At least you didn’t run aground."

Does that happen often? "All the time. Someone’s stuck at the bottom end of Loch Lochy now, and taking on water after putting a hole in their boat. We’re just off to rescue them."

Don't we feel proud of ourselves for returning all in one piece then? Sailing is a beautiful, beautiful way to see some of the most impressive scenery in the country and the sense of achievement as a novice sailor is quite something.

I've remembered a second rule – take any mishaps with a dose of humour. That way, you'll sail through.

A seven-night, self-catered cruise, starting and finishing at Le Boat’s base at Laggan on board the Elegance, sleeping up to six, from April is from £1,793 per boat/£299 pp. Le Boat (023 9280 9124,