Since when did the Bistro have a cellar?

It suddenly appeared when they needed somewhere to imprison David. A bit like how the houses expand when a family member comes home or a new lodger arrives.

Actually it makes sense for a bistro to have a cellar to store wine. The only problem is, the Bistro was built under a railway arch and railway arches don't generally have cellars. It would have been hugely expensive to dig out a cellar when the Bistro was built, and I doubt Nick could have afforded that at the time.

When Robert was living there after he left Tracey (actually, is he STILL living there? where does he live?) he lived in the storeroom where all the stuff was. Now suddenly there's a cellar! Perhaps the former storeroom has been converted into Robert's bedroom 

I am ANYTHING but a pugnacious upstart

At least they've now admitted it, on their Facebook page tonight-

"We bet you didn't know that the Bistro had a cellar!
(That's because we only just built it, especially to lock up David...)"

Then pictures underneath of the plans they drew.

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