No I get that and if he wants something to just have a laugh on, then you and Dammit are right. But as I say, knowing Hippy, he may well fancy riding it across an entire country or continent in one go and not Peaslake.
In which case speed and comfort would be better than chuckability and radness
There are plenty of bloody good MTB trails close to London. If he wants to just bridleway bimble/smash, I question the need for an MTB at all