I was stripping this block for parts and looked again at the original issue which I thought was a crack when the engine was still in the car and it wasn't so easy to see (it was a December evening!) - I can see now that the liner has slipped and as this is a 3.5 Rover V8 which this isn't really supposed to be a problem on according to all I read I thought I'd post a few pictures - as per the title, the engine number starts 24D.
This shows how far the liner has slipped down:

this shows the track to the water jacket that has been able to form through the aluminum which is unprotected by the liner.

and in this you can also see that it looks as if at about 7 o'clock something has given the block a clonk and burred the edge of the aluminum casting over as if to hold the liner down - can't see much point in that!! - there are also a couple of fainter tracks etched in the block heading towards the waterway.

My main reason for posting was for interests sake and to flag that 3.5's do drop liners - I don't know the history of the engine other than when it came to me it was in a Discovery with LPG. Maybe it had overheated at some point.
Dave