uPVC window catch won't shut, getting draughty!

[epimenides]

The handle on the uPVC window in the house I've just moved into won't turn. The window doesn't form a seal against the frame so it is getting cold in here! I've noticed that there's a small metal pin sticking out of the handle fitting. On another (working) window in the house, this metal pin is flush with the handle fitting. Here are some pics for comparison:
Bad window:
View media item 56517Good window:
View media item 56518
What is this metal pin? Is it kind of safety catch? If so, how do I release it?

If the pin isn't the problem, how can I get this window to close properly? There are no screws to undo the handle. The locking mechanism seems to be via two sliding bolts.

Thanks for reading!

 

[epimenides]

WD40 on the moving parts hasn't helped.

Can anyone at least advise me how to seal the gap between the window and the frame to keep the heat in?

 

[kbdiy]

Try tapping the pin fully into the handle. It's used to secure the handle to the spindle.

 

[epimenides]

The pin won't move and I suspect that the window's moving parts have rusted beyond salvation and need to be replaced.

In the meantime I have taped up the window with cardboard...