Muhammad Yahia, 14/01/2014 16:50:
"The person who is 'sponsoring' your visit cannot give a guarantee that you will comply with the terms of your visa, or*that you will leave the UK at the end of your visit*.
Then it's easy, we ensure they have a return ticket and we promise block on all Wikimedia projects if they don't leave UK. It's like capital sentence, who wouldn't comply?
Nemo