thanks steve - very interesting.

This is no doubt technically correct - there is no written evidence.

However, I'm sure I've read this area referred to as 'hallowed ground' - sorry no reference - but it was early 20 century, so this is no recent invention.
It suggested it was common knowledge - (perhaps as local folk law).
Since few could write before then, should we so lightly dismiss this 'evidence'?

Also consider this: this land is a remote part of the Dulwich estate - if the estate had 10 to 50 infectious bodies to dump in ~1349, this is a reasonable location. I doubt that you were allowed to bury infected bodies in other people's estates after all.
It is reasonable to think London Rd existed then, following the boundary of the estate, but not going any where in particular, so this site was remote yet accessible (!).

And this was no one off event - plagues hit every 20 years until the mid to late 17 century - so that is plenty of time for the oral tradition to get established.

Should there be an investigation ie a dig?

Frankly if there is potentially live plague virus in a bone down there, (the best historical/scientific outcome), surely it is safest that it stays there and rots for another 400 years.
Most likely outcome by far would be that nothing would be found, which would not prove anything either way.

So I am happy to stay in the dark on this one.