p.k. wrote:
but it seems sensible to apply the same keep left rule by convention

Yes and no...

On the stretch through Hyde Park (where the path is quite wide) peds
and cyclists are "separated" by a thick white line. Here, "keep left"
does seem to be the de facto rule and it mostly works quite well.

But on the stretch through Kensington Gardens (where the path is not so
wide), there is no separation of peds and cyclists so it is really a
case of riding a little more cautiously, and choosing whichever side of
the path is safest at that time - and definitely not being dogmatic
about which side of the path you pass on. A little courtesy is all it
takes to keep everyone running smoothly and safely.

In my encounter this morning, it was the idiotic behaviour of one rogue
cyclist that caused a problem, not whether or not I was on the left or
right side of the path. (The fact that I /was/ on the left is
irrelevant.)

All that said, I'd be happy for "keep left" to be made an official
rule, as long as it could be enforced, and as long as it also applied
to pedestrians.

d.