Thread resurrection:
Shame on you lot telling the OP to just 'buy another string' !
This is my kind of thing; inventive, creative, ecologically aware, and above all cheap. Oh and it saved me yesterday. Set of second hand strings, one already cut too short. Guy I bought them from too tiresome to talk to so I needed a cunning solution and here it is. Thank you @tommorichards (if you still exist)