(Reuters) - Car insurance premiums in Britain fell by an average of 1.1 percent in the third quarter of 2017, the largest quarterly fall in more than three years, according to the Confused.com car insurance price index and Willis Towers Watson (>> Willis Towers Watson PLC).

The price of an average annual comprehensive motor insurance policy fell to 838 pounds, 9 pounds lower than in June, Willis Towers Watson said in a statement, after Britain announced plans last month to change the rate for calculating personal injury payments, a move expected to cut the size of the payments.

The latest plans for the personal injury rate come after an unexpected change in the rate earlier this year pushed up the size of the payments, denting insurers' profits and driving premiums to record highs.

Admiral (>> Admiral Group), Direct Line (>> Direct Line Insurance Group PLC), esure (>> Esure Group PLC) and Hastings (>> Hastings Group Hldg PLC) operate in Britain's highly competitive motor insurance market.

(Reporting by Noor Zainab Hussain in Bengaluru, editing by Louise Heavens)