Big cars wearing mass-market badges have a reputation for heavy depreciation. And despite its niche status, Vauxhall's Signum proves the point. The flagship model, based on a stretched Vectra platform, stands alone as a large executive hatchback, and has struggled to establish itself among more mainstream rivals. That makes the car an amazing bargain on the used scene.
The front and interior are very similar to the Vectra's. Only at the rear of the cabin are there differences, with executive-standard legroom for two, fantastic seats and an optional 'Travel Assistant' system, which offers a power point, fridge, lockers and other clever stowage systems. All this makes the Signum a practical and comfortable car.
But the Vauxhall badge has harmed values, which are in line with those of the Vectra. So the Signum is cheap to buy - and economical to own and run, if you choose engine and trim carefully.
* Gearbox: first and reverse are notoriously tricky to engage on manual cars. This is a characteristic rather than a fault, so don't let it put you off, unless there's a grinding noise when you select the gear.
* ECU: problems are indicated by a glowing yellow 'spanner' on the dash which, on DTI models, can indicate turbo trouble. Get a diagnostic check carried out.
* Engine: premature engine wear can develop if the 2.2 DTI is gulping oil - look out for noisy clatter at start-up and a smoky exhaust under hard acceleration.
* Seats: the clever rear seat incorporates a central console, but it can be hard to remove and refit. Clips are known to break, leading to rattles from the rear of the cabin.
* Electrics: a few niggles can creep into the complex wiring. Ensure all powered equipment works properly, especially the windows, sunroof and climate control.
With its stretched wheelbase, the Signum builds on the Vectra's impressive ride, and is a pleasant, user-friendly car with decent handling. All petrol engines impress, particularly the 2.0-litre turbo, but the V6 is thirsty. While the 2.2 DTI diesel isn't a good prospect, given its under-par economy and refinement, the 3.0-litre CDTI is pacey and frugal, and works best with an automatic gearbox.
Buyers have failed to identify with the Signum, so used values are no better than the Vectra's. Prices could well fall further as more arrive on the second-hand market and stocks build up. Diesels are a better option in terms of depreciation, if not driver appeal, and their insurance rating is four groups lower than the 2.0 turbo petrol model. But buy a Signum to keep - if you don't hang on to it for a few years, you'll be hit hard in the pocket by the loss in value. Jeff Paterson, senior editor, Glass's Guide
Life With A Signum
I got a great deal on my Signum when I traded in my Vectra, saving more than £2,000 on list price. It's amazingly practical and perfect for my family, but I wish I had opted for a more powerful engine. Jim Bennett, Walthamstow, London
My firm replaced its Omegas with Signums, but I prefer the older car. The Signum is roomier and the seats are better, but it's not as good to drive. Dale Burnham, Kegworth, Leicestershire
A mix of hatchback, coup