G-BCLO Sikorsky S-58ET of British Airways Helicopters - 1975
This picture is taken at the then British Airways Helicopter Engineering base at Gatwick Airport South (most famous now for the historic Beehive Air Terminal). The Aircraft shown is a turbine development of the original piston engine version of the S-58. In the UK Westland developed the S-58 Design for Military use as the Westland Wessex. Whilst some S-58T and S-58ET Helicopters were used by Civlian Operators, Bristow were the only operator to ever use a civilian Wessex!
The following Wikipedia Link primarily covers the Military Versions and use of the S-58 and its many derivatives:
Sikorsky H-34 (S-58 et al) - Wikipedia Entry