Door lock problem

[ajrtd]

This door hasn't been opened very often since it was installed over a year ago.
It was opened a couple of days ago and won't lock now.

How do I get the thumb latch off so that I can remove that locking mechanism.

TIA

 

[foxhole]

Philips head screw on door edge inline with lock barrel should release it.

 

[ajrtd]

It was this cover that stopped me removing the lock as its a very tight fit. I had to use a wood chisel to pry it off.

 

[big-all]

its worth checking the keep on the frame incase it or the other locating brackets have moved out off line
does the door mechanism work ok when fully open and not trying to fit in any frame fixings??