Bike wont unfold after fixing rear puncture

[Ben Lock]

After finally fixing a rear puncture by replacing inner tube (had to do valve through hole first) the bike now won't unfold. The rear shaft leading to the wheel gets about 1/2 way then jams. I suspect it's a chain or brake problem. The bike will fold up OK after I refitted the brake.

I've tried removing and replacing the brakes and wheel twice but no good.

Any ideas?

[Ben Lock]

Found problem - brake cable horribly caught on some plastic. Now stretched beyond usefulness.

TIP - never undo brake assembly while bike is unfolded!