How do I lock my Quinny Buzz

[PurlyQueen]

Help!

I won a fabulous Buzz on eBay but I can't work out how to keep it locked when I fold it flat and it keeps unfolding itself.

Any suggestions on how to keep it locked?

Standing behind it with the handlebar in front of IYSWIM on the left hand side there is a little rubbery dangly bit that hooks on to the left hand wheel where there is a knob bit to attach it too with a loop.

Thank you!