Personnel Index - Detail
There is no record that this airmen flew operations with 49sqn.
Sgt Sieve was killed in 14th January 1942 whilst flying with 207Sqn.
He is buried in the Failsworth Jewish Cemetery near Manchester.
The reference given on the CWGC site seems not to match the layout of the cemetery. However, thanks to research by Colin Cripps and courtesy of John Sharp we have received an image of Leonard's grave and more details of his loss.
Mancheter L7523. Note the unpleasant ground conditions requiring wellington boots.
Extract is from Bill Chorley's Bomber Command Losses
The excellent SKEALS website (The Spurn, Kilnsea and Easington Area Local Studies Group) has a webpage dedicated to this crash and the memorial which was subsequently erected.
Research carried out by the 49Sqn researcher with John Sharp has unearthed a great deal of information about Sgt Sieve.
In 1939-40, Leonard Sieve arrived in England from South Africa with his wife Joan. It would appear that in the UK they had a son, Clement. 
Whilst in the UK Leonard joined the RAF and served with 49 Squadron before being killed in action with 207 Squadron on the 14th of January 1942.
Details of the raid on Hamburg where Sgt Sieve was killed (click for a clearer version).
After Sieve was killed his family thought that it would be safer for Joan and Clement (Son) to return to South Africa.
Joan and Clement were to take passage on the SS Gloucester Castle. SS Gloucester Castle was part of a section of twenty-four vessels comprising convoy OS.32 sailing on to the Cape and beyond.
On the 15th of July 1942, whilst on voyage from Liverpool to Table Bay with 12 passengers, 142 crew and six gunners, she was shelled and sunk by the converted German merchant raider and auxiliary cruiser, Michel, about 840 miles west of Luanda, Angola.
Captain H.H. Rose and 92 passengers and crew were killed, including Joan and Clement.
SS Gloucester Castle
Michel's commander, Captain Helmuth von Ruckteschell chose to attack after dark without warning. The first shells from the Michel destroyed the bridge and radio room, consequently no SOS was transmitted. Two lifeboats containing 61 people were picked up by the raider and taken to Yokohama, Japan as prisoners. Two of whom died in captivity.
Due to his cruelty and method of attack on merchant ships, von Ruckteschell was tried in 1946 as a war criminal. He was sentenced to ten years imprisonment on charges of mass murder but died in 1948 of a deteriorating heart condition in Spandau.
Joan and Clement Sieve are both commemorated by the Commonwealth War Graves Commission (Civilian Section).
Click this link to read a very interesting and detailed account of the raid compiled by John Sharp