The Javelin experienced a protracted development period and did not enter RAF service until 1956. Progressing through nine operational marks, the Javelin proved to be more than capable of intercepting the Canberra at altitude. To keep pace with increasingly better performing Soviet bombers, the fighter's engines were progressively upgraded from 8,000 lb each in the Mk 1 to 12,300 lbs of thrust in the Mk 8. The Javelin remained the RAF's sole all-weather fighter until the arrival of the English Electric Lightning. Operating alongside the Lightning, the Javelin was retired from operational service in 1968 although one machine, now on display at IWM Duxford, remained in service with the A&AEE until 1975.