Dave Halliday came and did the second half of the Dumb Run with us on his and nearly didn't make it, but that was because his spokes kept exploding, Munky's fettling skills were all that kept him on the road.
Yeabut that one's a tortured mutant Brommie.
This is a good point, though. I'm assuming a Brompton will be as good for me as those who do epic adventures on them, and it might not be, so another good reason to go for a test ride first.
I've been known to say that the ideal Brompton ride is a couple of miles of gentle uphill to the station.
I have a fairly low opinion of anything with a saddle, and the Brompton's 'adequate' braking system compounds those inherent ergonomic failings. But their convenience means they score highly on the tool-you-have-to-hand factor. Cycling is, in general, a lot better than Not Cycling
[1], and Bromptons are fantastic at enabling that in a world infested with Bloody Trains, bike thieves, small cars, London flats, and similar obstacles.
To be fair, they are rather good at nipping around in an urban environment. Preferably one that's pothole-free, and not infested by impatient motorists (who in general seem to regard Brompton riders as stationary objects that aren't there).
[1] Especially Running and Buses.