Bond yields move inversely to bond prices.
For the first time, yields on one U.K. Gilt, which matures in March 2018, tipped into negative on Thursday. This means in effect that Gilt holders will pay rather than receive interest on government debt.
On Friday, two-year Gilts crept higher to yield 0.179 percent.
"The U.K. is now officially through the looking glass, as the Brexit vote has pushed Gilt yields below zero for the first time. Remarkably markets are now expecting interest rates to lurch downwards, despite already being at record lows," Laith Khalaf, senior analyst at Hargreaves Lansdown, said in a report on Friday.
Gilt yields accelerated losses on Thursday after Bank of England Governor Mark Carney said the central bank would probably ease monetary policy over the summer. That would be as a result of policy uncertainty and a tighter financial environment following the U.K.'s vote last week to leave the European Union.