This 4-6-2 express tank, which emerged from the workshops in 1910, was unlike any Brighton locomotive beforehand and was fitted with inclined outside cylinders, as on his Atlantics. The 6' 7½" diameter driving wheels, a large boiler with 170lb pressure, a bunker holding 3 tons of coal and tanks that held 2,300 gallons of water all contributed to making it the largest express passenger tank locomotive then built for the LBSCR (until L Billinton's Baltic tank of 1914), weighing in at some 86 tons in working order.

The second engine of class J was not built until 1912, after Marsh's departure from the LBSCR, and was N°326 Bessborough, though originally she was to have been named Grosvenor. (This latter name was subsequently used for one of the Pullman cars operating on the LBSCR). N°326 was not identical to N°325 in that she had outside Walschaerts valve gear and reduced capacity tanks holding just 1,989 gallons.

Both engines earned their living working the heaviest Pullman trains on the main line but in later years, in the twilight years of the Southern Railway, found themselves based at Tunbridge Wells working traffic on that line and the Oxted Line.

Both locomotives had alterations to them during their working lives, Bessborough's cab was altered in 1913 and after the grouping the chimney and dome of each locomotive were cut down to fit the new Southern Railway's loading gauge. This was done quite aesthetically, which is more than can be said for the treatment meted out to some other es-LBSCR locomotives! Both engines lasted into early BR ownership, being withdrawn in June 1951.