Brake keeps locking on Maclaren techno

[codandchipstwice]

Hello - my brother has given me thier old Maclaren as ours totally given up the ghost, whilst waiting for my micralite. It's in ok nick other than the brake doesn't click off - and keeps locking on. it makes a clicking noise when you engage the brake - but doesn't make the noice when you take the brake off. If you try and use it it's juddery until the brake locks fully and it won't move at all.

Nothing obvious I can see - any ideas??

Cheers