The first of the rebuilt Bullied ‘Merchant Navy’ class locomotives, No 34018 British India Line, hauled its first passenger service on 17 February 1956.
The original ‘Merchant Navy’ class Pacifics had been introduced in 1941 and a total of 30 of the type were constructed between 1941 and 1949; the lighter ‘West Country’ and ‘Battle of Britain’ classes, of which 110 in total were constructed, were built between 1945 and 1951. As designed by Bulleid, all 140 locomotives were fitted with air-smoothed cladding over the boilers. The Bulleid-designed valve gear, which was a modified version of the Walschaert valve gear, was driven by a chain — rather than gears as originally planned by Bulleid — embedded in a sealed oil bath. The driving wheels were of the Bulleid Firth Brown-developed cast steel which had been designed by Bulleid and developed by the Sheffield-based company Firth Brown. The boilers on the ‘Merchant Navy’ class were welded; those on the light Pacifics riveted. All were originally designed to operate at 280psi, but this was reduced in operation to 250.
Although successful, there were problems with the locomotives. For example, the driving wheels had a number of drawbacks. They were difficult to maintain, the hollows collected undesired particles like oil, sand and water, and were found to be prone to cracking. The latter factor was later attributed to the poorer quality of available steel used during and after World War 2 than to some intrinsic design flaw. More significantly, the engines had problems with the enclosed valve gear with oil leaks causing slipping and the occasional fire.
However, it was an incident at Crewkerne on 24 April 1953 that was to lead in part to the design to modify the class. On that date No 35020 Bibby Line was approaching Crewkerne at speed when the crank axle of the central driving wheel fractured. Although no-one was injured, the decision was taken to withdraw temporarily the entire class whilst the cause of the accident was investigated. Upon examination, it was discovered that the fracture had been caused by metal fatigue and that this was a common problem. As a result, all 30 of the class were taken out of service whilst a replacement crank axle was designed.
This issue, along with the other problems that had emerged operationally with the class, led BR to decide to rebuild all of the class. Drawing upon experience learnt with the BR Standard classes, then under construction, Ronald Jarvis undertook the redesign of the locomotives. The redesign saw the air-smoothed casing replaced by conventional boiler cladding whilst the chain-drive valve gear was replaced by three sets of convention Walschaerts valve gear. A new cylindrical smokebox was fitted as were new chimneys, similar in design to those fitted to the ‘Lord Nelson’ class, and LMS-style smoke deflectors. The Bulleid-designed steam reverser, which had proved fast-moving but unpredictable in operation, was replaced with a more traditional screw-link version. Other modifications included the relocation of the mechanical lubricators to the footplates alongside the boiler sides and sanding gear added to the leading driving axle. The BFB-pattern wheels were, however, retained.
The modified locomotives were to prove very successful although destined, unfortunately, for a relatively short life in rebuilt form. The use of the smoke deflectors with conventional classing eliminated the problem of visibility that had plagued the Unrebuilt locomotives, for example, whilst the modifications eliminated many of the maintenance problems that had afflicted the class from new. There was a new problem, however; this was that the Rebuilt locomotives placed a greater load upon the track. This was the result of the hammerblow caused by the balance weights on the outside Walshaerts valve gear; the original valve gear had avoided this problem by being largely self-balanced. The Rebuilt locomotives did prove excellent in service; the last recorded main-line run of a steam locomotive at over 100mph on British Rail occurred on 26 June 1967 when No 35003 Royal Mail achieved a speed of just under 106mph running between Winchfield and Fleet with an up service from Weymouth to Waterloo.
The programme to rebuild the Bulleid Pacifics commenced contemporaneously with the decision, as described in the Modernisation Plan, to phase out steam traction on Britain’s railways and replace it with diesel and electric motive power. On the Southern Region, much of the network was to be modernised through the extension of the third-rail network. Thus, whilst work on the conversion of the Bulleid Pacifics continued, work was also in hand in the planning of electrification. Although the programme of rebuilding the ‘Merchant Navy’ class was completed, with the last example, No 35006 Peninsular & Oriental SN Co, being completed in October 1959, only 60 of the light Pacifics were rebuilt before the programme ceased with Nos 34104 Bere Alston and 34109 Sir Trafford Leigh-Mallory, in May 1961.
With the rapid decline of main-line steam, the Bulleid Pacifics — both Unrebuilt and Rebuilt — were destined to have a shorter life than might have been expected. Withdrawal of the Rebuilt ‘Merchant Navy’ class commenced in February 1964 with the demise of Nos 35002 Union Castle and 35015 Rotterdam Lloyd, but 10 remained in service at the end of 1966 with the following surviving until the end of Southern Region main-line steam in July 1967: Nos 35003 Royal Mail, 35007 Aberdeen Commonwealth, 35008 Orient Line, 35013 Blue Funnel, 35023 Holland-Afrika Line, 35028 Clan Line (preserved on withdrawal; the only example preserved initially) and 35030 Elder Dempster Line. Of the 60 rebuilt light Pacifics, withdrawals again began in May 1964 with the demise of No 34028 Eddystone. A total of 29 remained active into 1967, with the following again surviving to the end of SR steam: 34001 Exeter, 34004 Yeovil, 34013 Okehampton, 34018 Axminster, 34021 Dartmoor, 34024 Tamar Valley, 34035 Whimple, 34034 Honiton, 34036 Westward Ho, 34037 Clovelly, 34140 Crewkerne, 34052 Lord Dowding, 34060 25 Squadron, 34087 145 Squadron, 34089 602 Squadron, 34090 Sir Eustace Missenden, Southern Railway, 34093 Saunton, 34095 Brentor and 34100 Appledore.
Of the rebuilt ‘Merchant Navy’ class, no fewer than 10 — Nos 35005/06/09-11/18/22/25/27/28 — survive in preservation, mostly as a result of being sold on withdrawal to Woodham Bros and subsequently rescued. Of these, the intention is ultimately that No 35011 General Steam Navigation will be restored to its original condition rather than as a rebuilt. An 11th, No 35029 Ellerman Lines, which was also sold to Woodham Bros, also survives but as a sectioned example for display in the National Railway Museum. Of the 60 examples of the rebuilt ‘West Country’ and ‘Battle of Britain’ classes, the following examples survive: Nos 34010/16/27/28/39/46/53/58/59/101. All of these were rescued from the Barry scrapyard; without Woodham Bros’s ownership, no rebuilt ‘Light Pacific’ would have survived.