Another Canberra mystery

Here’s another Canberra mystery which I can’t get my head around…

Canberra PR9 prototype WH793 appears in various photographs complete with tip tanks which are attached to the original B2 points (as was the case with all subsequent PR9’s of course), the extended wing tips reaching out beyond the tank positions. But later pictures of the same aircraft in RAE service show the aircraft with tanks attached to the extreme wing tips. Naturally, I was inclined to think that the aircraft had simply had the original B2 wing tips re-attached but photographs taken from different angles suggest that the tanks are indeed fitted to the extreme tips of the extended PR9 wing tips.

So, I wonder if anyone might have a clue why this might have been done? What possible point would there be in re-attaching the tanks further out on the PR9 wing tips? A strange business indeed!