You are quite correct, Adrian. I'd not checked the kit which is the subject of this thread properly, and didn't know that Walsworth did a Y1 and a Y3. Here's a photo of the propotype 8400 followed by a full description by Mike Bootman of the GER Society to whom I remain indebted for the amount of work he did on identifying both loco and confirming the location.
Brian
8400 LNER Y1 Class Sentinel. Date approx 1935. Lowestoft Harbour. Notes by Mike Bootman follow: Lowestoft Harbour - alongside the Trawl Dock with Waveney Road in the background. The Eastern Counties Railway and later the Great Eastern Railway undertook a considerable amount of development and expansion of the Harbour and consequently it was well served by rail. As well as serving the Outer Harbour Trawl, Waveney and Hamilton Docks on the north side, at the easternmost extremity of the outer wall there was a sand extraction plant. There were also comprehensive sidings to private works and factories on the south quay of the Inner Habour, together with the railway's own Yards, Works and Sleeper depot n the North Quay. Class Y1 Sentinel CE (Central Engined) Loco No. 8400 (first of the type) shunting GWR wagons on quayside. The locomotive is the first member of Class Y1 Sentinel CE (Central Engined) Loco No 8400. It was the first of the type purchased from Sentinel in 1925 for evaluation, the LNER having in May 1925 tested a similar one on the Derwent Valley Railway using it's Dynamometer Car. Sentinel claimed that this design used less than half the coal and water, and cost less than half the amount to maintain and repair than a conventional locomotive. Furthermore it's short wheelbase and light axle loading permitted its use on sharply curved and lightly laid lines. The locomotive was delivered to Lowestoft in September 1925. Following its first six months operation it was estimated that it saved £158 (£316 per annum) compared to a conventional steam locomotive and, at a purchase cost of £1400 this was clearly a very good return on the investment. Consequently the LNER purchased a number more of two different types (and vatrious sub-types) classed as Y1 and Y3. The profile of this locomotive, originally numbered 8400 on taking into stock at Lowestoft on 27/9/1925, was different to all of the following ones in that it was taller, had a radiused sheet metal fillet on either side between cab front and tank top, different frames and various other elements which make it readily identifiable from the others. It is just possible to make out the No. 8400 on the lower cab side. It spent the whole of its working life at Lowestoft, being renumbered 7772 on 1/4/1943, 8130 on 12/1/1947, and finally Departmental No. 37 on 26/4/1953 before being condemned on 31/1/1956. At some unknown date, before the photograph was taken, the short handrails either side of the cab were extended downwards. It is just possible to see the location of the original fixing mid-way between the running plate and the beading level with the tank top. It travelled to Stratford just the once for a General Repair, between 19/12/1936 and 21/3/1937, thus supporting the manufacturer's claims of economy. Its main duties were in and around the Sleeper Works but also involved trips to the North Harbour area, where it is seen in this photo heading alongside Wveney Road towards the Fish Docks. Given the lack of interchange traffic with the GWR it's interesting to note that the goods wagons it is hauling are all, bar one, clearly marked with that company's ownership. The van beyond on an adjacent line is an ex-GCR 10T 18' Fish Van, which is coupled to an early LNER design 10T Fish Van just visible behind the Y1.
Personal collection. Photo by the late Arthur Dudley Neg ID No 40. FINAL