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I quote:    This is the most extraordinary  convoy of the WS  series of convoys,  and possibly the most interesting convoys of WW2.

The British 18th Division  arrived at Halifax, Nova Scotia  in early November 1941  and   embarked  on United States Navy troop ships.
Their initial destination was believed to be Basra.

Note that  the United States    was still neutral at that date.       
See www.naval-history.net    and then search for WS  convoys
Lord Haw Haw  seemed to know about their voyage across the Atlantic towards Capetown.   It was  transmitted  from the Tannoy of one of the ships  that their  Troop ship  had been sunk.

The second battle of El Alamein started on 23 October 1942, about two weeks later the Axis forces, both German and Italian started a full retreat. Often the Germans would leave the Italians behind.

Elements of the allied forces went L for leather after the axis army, collecting prisoners along the way. So examine what the records say for November and December 1942.

It says somewhere on his record that he was Lines of Communication supply.  RASC would be transporting the fuel.

Secondly, he may have embarked for Italy further west than Egypt

Can you  read the message displayed on the signal flags?

The top photo of L19 I think shows them on deck for leaving port

The  addition of "P"    could denote  that part of the convoy   branched off  at  some point.     Possible   that P   may stand for "Persia"   for example? 

Added     Google search  on WS  convoys   gives  a fund of detail