In message .com,
Londoncityslicker writes

Are those the Hounslow loop services which go via Richmond then round
to Hounslow.

Yes - on the last part of their clockwise journey round the loop.

The ones which aren't really advertised (I guess to stop people getting
really confused)

Well, they're advertised clearly enough in the Housnlow Loop timetable,
but circular services are always a problem for simple destination-board
signs. Or for queries like "Does this train go to Chiswick? Well, yes
.... eventually"!

Of course the other use is to getting over to Richmond, Sheen or
Mortlake easily.

Obviously works in the other direction too. But I don't know why the
residents of Richmond would ever want to come to Hounslow!

I think the clockwise service is provided to enable residents of
Hounslow to get back
--
Paul Terry