British ​government bond ​yields fell to their lowest ​since mid-August on Tuesday and were on track for their ‌biggest one-day ⁠fall ⁠in three weeks after ​oil prices dropped as investors shrugged ​off the latest U.S. sanctions campaign against Iran.Ten-year gilt ​yields fell by ⁠as much ‌as 5 ​bps ​on the day to ⁠5.01%, their lowest since August ​14 and heading for their ​biggest one-day decline since August 4, after a $3 daily drop in the price of ‌Brent crude.The move was broadly in line ​with ​a drop ⁠in U.S. Treasury yields .Thirty-year gilt yields also hit their lowest since August ​14 earlier at 5.739%, down just over 5 bps from Monday's close.