As a start point for you, the Unaccounted Airmen thread on the RAFCommands Forum has him listed as:

MELLISH, John Thomas – Sgt (A/G) – Wellington X – HF480 – 11 OTU.

Also just found this information:

T/O 1955 hrs from Westcott on nickelling operation to France using call sign MZL E. Having safely completed their primary objective the crew then proceeded, as instructed, on a navigation exercise. While on this phase the Wellington ran low on petrol and the crew called up Little Horwood and requested permission to make a precautionary landing. En route, having been given clearance the engines began to splutter and the order to bale out was given. Only two were able to comply before the bomber dived to the ground at 0235 hrs, crashing amongst trees just short of Little Horwood’s runway and broke up

Regards

Pete

Sorry, can’t help on the “SI” test, but thought it might be worth noting that both of the No. 35 Squadron aircraft participated in the “Goodwill Tour” to USA in 1946 (with TW870 crashing on its return to the UK as mentioned in the previous post). I have been in contact with one person who actually flew in TW870 whilst with the squadron.

Regards

Pete

Charlie

I found this, which may be a useful start point (although I have not had the chance to verify the information):

“The final point of interest that I noted on my dander was a small monument made from the propeller blade of a Lancaster Bomber from 44 (Rhodesia) Squadron RAF. On the night of the 19th/20th May 1944 a large scale bombing raid was mounted against Amiens railway station but the weather was so bad that the attack was aborted. Lancaster ND689 KM-O however never made it home crashing into one of the lakes. Five of the crew were killed and the other three captured.

In 1995 the Air Association of Le Bourget began searching the lake and over the next few years dragged up three engines, various other bits and pieces and five bombs! Rather unusually three of the crew including its Canadian pilot, Flying Officer Robert Barber are buried at Abbeville whilst one of the others (WO2 Donald Scott — another Canadian) is buried in Amiens. The only Rhodesian in the crew, Pilot Officer Stuart Ingram is commemorated on the Runnymede memorial”.

[Source: http://www.smg-authie.co.uk/txtpat/index.php?id=25%5D

Regards

Pete