Very grand designs, but who needs a ginormous £30k sofa?

Your starters for ten: what is a ‘ghost bullet’? When would you use ‘aluminium foam’? And why would anyone pay £30,000 for an ‘infinity sofa’?

I’m used to watching whole editions of university Challenge or

only Connect, and being unable to answer a single question. But to discover I require Google for making sense of crime dramas and architecture shows has left me with a new sense of inadequacy.

Even though I now know, thanks to Extraordinary Extensions (C4), that an infinity sofa is a segmented settee bigger than a kingsize bed, I still can’t see the point of spending more than the price of a brand-new family car to own one.

However luxurious, however sprawling, a sofa is still just a place to park your backside.

Professional gambler Simon and his teacher wife Amy certainly had the elbow room. The home they were renovating in Herefordshire consisted of three buildings — a disused water mill, a coach-house and a cottage. They had 4,000 square feet of floor downstairs... and that was before they doubled it by connecting the houses with glass-walled bungalows.

Presenter Tinie Tempah called it ‘one ginormous family home’. That’s putting it mildly — this was a residential complex, a 21stcentury country house. Tinie, better known as a rapper than an architectural student, revealed a confident knowledge of property developing.

He had doubts about the immense glass panes, 19 of them, on order from Portugal for £179,000. And he was right to worry — when they were slotted in, they leaked.

That’s why we watch these shows, of course. No one is looking for inspiration for their own millionpound projects, but it’s fun to squash up on our very finite sofas and predict disaster . . . before being proved wrong, of course.

The aluminium foam cropped up at the back of a suburban house in South London, where the owners wanted a replica of the Alps mounted above their kitchen.

To keep the roof from collapsing under the weight, they commissioned the sculpture from honeycombed metal, like an aluminium Aero. Indoors, the worktops were made from blowtorched plastic.

‘So trippy,’ said Tinie in approval. ‘one hell of a ride.’

Ghost bullets, meanwhile, spelled violent death for a solicitor in Lerwick, as the windswept murder mystery Shetland (BBC1) returned.

That’s shooter jargon for untraceable ammunition, machined in a garage workshop and usually intended for antique weapons. The lawyer was shot with a 1944 Walther P38, standard issue in the Wehrmacht during World War II. Maybe there’s a Nazi stormtrooper holed up in the Northern Atlantic, who hasn’t heard the war is over.

Shetland is a subtle, multi-layered drama, and that word ‘ghost’ held many meanings. Detective Jimmy Perez (Douglas Henshall) was mourning his mother, and trying to cope with his father’s worsening dementia — a forgetfulness that was slowly turning the old man into a walking ghost.

The full cast is back, including Alison o’Donnell as Tosh — the sergeant who was once a seething heap of radioactive romances but who now has matured into a wise voice. I liked her better when she was falling to bits.

unlike other long-running crime shows, Shetland has always striven to be low-key — not entirely plausible, but rarely ridiculous. It took a wayward turn, though, when a diver and potential witness was trapped inside a decompression chamber, before all the air was sucked out.

A nasty way to go, and wildly unlikely. I hope Shetland isn’t turning into Midwinter Murders.