A purchase from an ebay seller came with this description "LMS double-headed freight 1950’s" but it was obvious that it wasn’t anything of the sort.
The scanned image immediately revealed that it is, in fact, The Night Ferry as the leading coaches, which are only just about visible, are CIWL stock. I posted a message on the SEmG Yahoo group's message board that posed many questions all of which, not unexpectedly, were answered swiftly and accurately.
This is, indeed, The Night Ferry photographed passing through the up platform at Folkestone Junction station. The engines are not individually identifiable but the pilot engine is a Maunsell L1 class 4-4-0 whilst the train engine is a D1 4-4-0. It's been established by a sharp sighted SEmG member that the L1's running plate is clearly 'lined out' which means that the shot was definitely taken pre-WW2.
The above set me on my own research path as I'd forgotten that I own a copy of Brian Haresnape's Maunsell Locomotives A Pictorial History which, on investigation, has been revealing. On pp 69 Brian writes: "The first ex-Victoria Night Ferry working took place on October 14th, 1936 and the motive power was L1 4-4-0 No. 1758 and D1 4-4-0 No. 1470." The up Night Ferry the following morming would have passed through Folkestone Junction at around 0700 and this begs the question: why would someone go out with a camera that early on what was almost certainly a cold pre-war morning to photograph a passing train unless it was to snap a new and very unusual train?
Many members of the SEmG group have contributed to the above caption: [Steph Dale; Pete Joels; Clive Standen; Tom Burnham; John Lewis]