disposal times and eliminating or mitigating one of the most unpopular jobs). The domeless engines Numbering started from 5000, with the first twenty being ordered from Crewe Works in April 1934, and a further fifty (5020–5069) ordered from the Vulcan Foundry in 1933. The first of the Vulcan Foundry engines entered service in 1934, and the entire order of 50 was delivered before the first Crewe-built engine, No. 5000, was completed in February 1935. The first 57 locomotives were built with domeless boilers with straight throatplates and a low degree of superheat (14 elements in two rows), the boilers of the remaining 13 (5007–5019) were provided with a three-row version (21 elements) having greater total surface area and giving less obstruction to gas flow. The original 57 boilers were converted later to higher superheat (24 elements) and fitted with a dome. Further orders were placed with Crewe (5070–5074), Vulcan Foundry (5075–5124) and Armstrong Whitworth (5125–5224) for a total of 155 locomotives which were also built with domeless boilers with straight throatplates and 21 element superheaters. All these boilers, including the early converted ones with a dome, were fitted indiscriminately to any of the first 225 engines, which could appear at various times with domed or domeless boilers. However, many of the early frames were converted to accept sloping throatplate boilers, as listed below. This modification was carried out to provide a stock of spare boilers for the early engines, which would minimise the time spent in works by engines awaiting a fresh boiler. All locomotives from no. 5225 were fitted when new with the sloping throatplate boiler. All extra boilers made had the sloping throatplate arrangement, and only one example of a later engine having been fitted with a straight throatplate boiler is known - no. 45433. Several different patterns of boiler were used on the locomotives, running into double figures. The throatplate design was the most significant, but there were also different numbers of superheater flues, firegrate arrangement, stay material, dome and water feed arrangements, washout plug placement, etc. in various combinations. The following locomotives were built with straight throatplate boilers, but were later fitted with a sloping throatplate boiler (date in brackets). Conversion was done by relocating the frame stretcher immediately in front of the firebox. Some of them reverted to straight throatplate at a later date, and these are also shown where known. Those marked with an