I've completed this puzzle - all but the empty cell at the centre. I just can't work out which letter should go in that space. Can anybody, please, put an end to my anguish......and explain why?
help please 11a eg orpiment from NZ,mined with care 6 ?A???? 13a river turns entering artificial lake-bridge now abandoned?7 PL??O?? lido?po? there somewhere? 15a glossy fabric lending special allure...