Analysts polled by Reuters had expected a 50 billion pound cash boost, or quantitative easing, from the central bank . However, some traders had speculated it might opt for a 75 billion pound injection, and possibly a cut in the bank rate.
Sterling rose to $1.5601 from $1.5570 before the BoE announcement, but remained well below this week's high of $1.5723. The euro was at 80.20 pence, compared with 80.36 pence before the move.
September gilt futures pared gains by more than 30 ticks to hit a session low of 119.19 after the decision. The yield on ten-year gilts rose by 4 basis points to stand at 1.712, down 1 basis point on the day.
Currency, bond, and stock markets also moved because of an unexpected Chinese rate cut that was announced around the same time as the BoE move.