USGW was a Hawker Siddeley Dynamics project to develop a submarine launched anti-ship missile. The project was based on a study called "Ondine" but eventually became based around a variant of theMartel missile that was in service with the RAF.
The weapon was to be stored and launched like a torpedo and on breaking the surface, the IMI tandem boost rocket motor ignited to boost the missile to a speed where the sustainer motor could take over.
Guidance appears to have been the same as the RAF Martel, i.e. TV, however, Marconi's participation in the project suggests that the Active Radar Martel seeker may have been used.
The project evolved into CL.137 Sub-Martel, but this was cancelled in favour of the acquisition of the McDonnel Douglas Sub-Harpoon from the USA.
Image at right courtesy of HSD / Janes shows USGW as it broaches the surface, discards its launch shrouds, unfolds the wings and ignites the tandem boost motor.