John Mayo is going head-to-head with his former employer in demanding a break-up Vodafone. Mayo was a mergers and acquisitions banker at SG Warburg, now part of UBS, which is house adviser to Vodafone and has worked on the bulk of its M&A deals along with Goldman Sachs.

The links between Vodafone and UBS have been strengthened by a series of ex-bankers working for the mobile phone company. Should Mayo enter negotiations with Vodafone, he will also come into contact with Warren Finegold, a former UBS banker who was appointed as group head of M&A at Vodafone last year.