A court has heard that manipulating Libor rates was so commonplace an offer of a Mars bar could get it changed. Tom Hayes, who worked for UBS and Citigroup ... is the first person to face a jury trial for manipulating the key interest rate, used to set trillions of pounds of investments. The court was shown ... transcripts of exchanges between traders using UBS's internal messaging system. The conversations all related to moving Libor rates, said Mr Hayes, to assist the traders' and banks' commercial interests, something he said he found it hard to see as wrong. In one chat, Mr Hayes suggests the market is rife with dealers attempting to influence rates: Very, very hard to price stuff with the fixes so manipulated and inconsistent." His correspondent replies: "The fixes are manipulated?" "Yes, of course they are," says Mr Hayes. "Just give the cash desk a Mars bar and they'll set wherever you want." He has alleged throughout his trial that ... senior managers, even the chief executive of the bank, knew all about it. He said he was "shocked" when his manager phoned him asking him not to mention Libor rate-setting in any emails. The court was also shown an email exchange between senior management appearing to show they had reservations about Mr Hayes. "Personally I find it embarrassing when he calls up his mates to ask for favours on high/low fixings. What's the legal risk to UBS asking others to manipulate rates?" The Libor scandal has seen a number of the world's leading banks fined for manipulating rates.