HERE’S an important safety tip: if you are going to have a car breakdown try to avoid the lion enclosure in a safari park.

But that’s exactly what happened to me last week when, for no obvious reason, the Legacy Sport Tourer refused start. Worse, it decided I was a thief and sounded the alarm whenever I tried to coax it back to life.

As you can imagine this put a bit of a dampener on the test which, until that point, had been going very well.

The Legacy - Subaru’s biggest car - is only available as an estate in the UK but that’s fine with me. The combination of permanent four-wheel drive, a big boot and the world’s only flat-four “boxer” diesel makes the Legacy Tourer a highly desirable combo - especially in the rural areas of County Durham and North Yorkshire.

You can still buy a Legacy with a 2.0-litre or 2.5-litre petrol engine but why would you when the diesel flattens both with its 258 lb/ft of torque?

A clean sheet design, the boxer turbodiesel is smaller and lighter than its petrol-powered cousins. The turbocharger gubbins and catalytic converters are fitted beneath the sump to lower the car’s centre of gravity (already a flat-four strong point) for better handling and control.

It makes a lusty 150PS at 3,600rpm. The 2.0-litre petrol produces the same horsepower - but not until 6,000rpm. Round one to the diesel then.

Of course, the 2.0 petrol is smoother, but not by as much as you’d expect, so it scrapes the second round.

The boxer engine design gets its name because each piston moves in and out simultaneously, like a pugilist touching gloves at the beginning of a fight. Boxers have a natural dynamic balance. Only a straight-six or a V-12 have the same inherent balance which ensures they run smoothly without the need for costly balance shafts or counterweights.

The Legacy’s diesel delivers a knockout blow at the pumps, where the TD is remarkably frugal - something that can’t be said of the flat-four petrols.

Subaru hasn’t gone down the stop-start route, added brake regeneration tech or fitted inappropriately skinny low rolling resistance tyres to make the most of every precious drop of fuel. Instead, it’s fallen back on the tried ‘n tested expedient of fitting an overdrive top gear.

When it arrived in 2008, the first generation Legacy TD had a five speed gearbox. The 2011 model has an extra cog, preserving the high-striding top gear but usefully shortening the gap between the intermediate ratios for better acceleration.

In sixth, the Legacy’s powerplant is turning over a lazy 2,100rpm at 70mph - that’s seriously tall gearing.

And it works. During the test I covered nearly 700 miles and returned an average of 48.7mpg - an excellent result for a big car.

The downside of the intergalactic gearing is the 2.0TD’s lack of any real oomph in top. When you’re slogging up a steady incline you have to change down to fifth, or even fourth, for instant acceleration.

If you listen closely there’s still a hint of the traditional flat four “warble” beneath the turbo whistle and diesel clatter. The engine gathers pace smoothly and cruises quietly. Most of the time, it just sounds, and feels, like a petrol powerplant. Overall, it’s a worthy member of the Subaru family.

Four-wheel-drive traction, sporty suspension and that low C of G make the Legacy an enjoyable car to drive quickly on B-roads. It feels well balanced and easy to place. The brakes are powerful and simple to modulate.

Inside, the cabin is nicely trimmed from quality materials. A colour touch screen monitor displays the sat nav map. The head unit plays DVDs as well as CDs. Interestingly, Subaru has dumped the Legacy’s frameless windows that had become something of a signature feature.

The boot is a handy 100 litres larger than the one you’ll find in the rump of a BMW 320D Tourer and the rear seats drop down at the touch of a button leaving a long, wide and low load space. The Subaru is also £1,500 less than the best-selling German.

As for the lion enclosure, I managed to get help from park security and, after a bit of head scratching, the car suddenly fixed itself. The alarm turned off and the engine sparked up just as suddenly as it had all gone wrong.

Later, the friendly chap from Subaru Assist diagnosed a temporary mismatch between the key fob code and the engine management system. He said it was the first time he had seen such a problem and suggested I’d just been unlucky.

Not that unlucky mate - after all, no one was eaten by a lion.

SPEC CHECK: Engine: 2.0-litre flat four turbodiesel.

Max power: 150PS @ 3,600rpm.

Max torque: 258 lb/ft @ 1,800 - 2,400rpm.

Max speed: 120mph.

0-62mph: 9.6 seconds.

Av fuel consumption on test: 48.7mpg.

CO2 exhaust emissions: 161 g/km.

Equipment: Electric windows, mirrors, satellite navigation, CD and DVD player, voice recognition, cruise control, heated seats, 12-volt accessory socket, alloy wheels, climate control, alarm, immobiliser, “keyless” start and locking.