And they are retro-fit-able so this
don't buy a Brompton before 2007!
only applies if you have
no mechanical abilities , but even then your Brompton Dealer, will fix that.
or any bike shop mechanic as I have done,* if you bring in the parts ( you still have to buy them through, the dealer)
I had a Mk 2, 3 speed from the mid 90's I did work on it , such as the catch, then resold it, improved, when I got another used, newer, one..
....