In message
ilgate.org, Troy
Steadman writes

Immediately to the north of the current line from New Malden to Raynes
Park is a "ghost" line, bridged and laid out as if for rails and now
connecting IMMSMC the former Water Works at Berrylands to London. Do you
know anything about that one?

On 19th-century maps it is an embankment marked "Lambeth Water Company"
- see http://www.old-maps.co.uk/ and look up New Malden.

I suspect it is simply a water main from the riverside reservoirs at
Surbiton (Long Ditton) up towards the company's reservoirs at Streatham
and Brixton - and that it just happens to be above ground at this point.
I can't see any sign that there was ever a railway on top of this
embankment - rather the railway and water main were built side-by-side.

--
Paul Terry