The Mystery ship is Lifeline, which was built in 1944 for the Admiralty as a coastal salvage vessel by Smith’s Dock, Middlesbrough and completed in February 1944. She was chartered to Risdon Beazley Ltd, Southampton in June 1947 and purchased by them in February 1959. She was not a conversion, and the only modification she underwent was the substitution of her original goalpost mast forward of the bridge by two derricks with the single mast and derrick shown in the photograph. She served mostly in home waters, including at Normandy in 1944, and in a varied career took part in the salvage of the submarine HMS Truculent in the Thames in 1950. She was broken up in Singapore in 1981.
A. J. Smythe, Rayleigh, Essex