I'm not suggesting driving it - I'm talking about a car parked at the end of his drive/garden that doesn't move
and ultimately an MOT only means that a car has been assessed as passing a set criteria at one particular point in time - you could drive away and fit a decat in the half hour after and make it "un-roadworthy" and I'm sure a lot of people do!
Not only that but I bet there's a lot of numpty drivers who have no idea that their shocks are shot to bits, or their tyres are bald and underinflated, or that they have a bulb out - I would say that as 'enthusiasts' we have more of an idea of what's an acceptable deviation from the official MOT definition of roadworthy! lol
Either way, you should definitely be insured! When I was working downstairs on collecting debt, some woman in a porsche spun off and hit a bridge, causing over £20k of damage - the insurance didn't cover her as her tyres were below the limit (so in effect she was driving without insurance) so she was going to have to pay for it herself! :S