Six decades on, the Tractors of the train world still delight the diesel rail fans

The North Norfolk Railway-based Class 37 on goods train approaches Weybourne station - in mid-1960s livery. Picture: PAUL GEATER (Image: Archant)

A third of the 308 locomotives built between 1960 and 1965 are still in existence - 68 of them still used for main-line operations.

Two of these have been used for several years on local trains between Norwich and Lowestoft or Great Yarmouth "top-and-tailing" three traditional carriages.

But now the clock is ticking on these services as Greater Anglia starts to take delivery of its brand new Bi-mode trains from Stadler. The heritage service on the Wherry Lines is due to come to an end (much to the disappointment of enthusiasts) over the next few months.

To mark this Greater Anglia is running a special train in association with East Anglia's Children's Hospice travelling over the main lines that were familiar haunts of the Class 37 from the 1960s to the 1980s.

A Class 37 at Dereham on the Mid Norfolk Railway in its Rail Blue livery from the early 1970s. Picture: PAUL GEATER (Image: Archant)

From Norwich the train is heading along the Breckland line to Ely where it will reverse to Kings Lynn before travelling the length of the West Anglia route, through Cambridge, to Liverpool Street Station.

After a short stop there it will return to Norwich along the Great Eastern Main Line through Colchester and Ipswich.

But once the locomotives are no longer needed on the Wherry Lines, they are unlikely to face the scrapyard just yet - the Class 37 is still very much in demand for engineering, logistics and some shorter freight trains.

Because there is no other type of engine that can do what the Class 37 can - and in truth many of those left in service have been rebuilt with new engine parts and power transmission systems put into the early-1960s body shell.

A visiting Class 37 in freight livery on the Mid Norfolk Railway. Picture: PAUL GEATER (Image: Archant)

The locomotives were designed to be "mixed traction" machines to pull both passenger or freight trains and with an output of 1,750 brake horsepower, they were medium-power. Their distinctive sound earned them the nicknames of "Growler" and "Tractor."

There have been no other locomotives built since they entered service to fill the same niche - modern freight diesels are all more than 3,300 bhp and are overpowered for much of the work still done by the Class 37.

From the late 1960s to the early 1980s they shared the main line Intercity services between Norwich, Ipswich and London with the more powerful Class 47s - and in truth the Class 37 was perhaps slightly under-powered for this fast route.

But they were the main locomotive used on the West Anglia main line for the services to Kings Lynn before that route was electrified. Unlike today, at that time most services from Kings Lynn ran through to Liverpool Street rather than Kings Cross.

The Epping Ongar Railway in Essex has a Class 37 in mid-1960s livery. Picture; PAUL GEATER (Image: Archant)

And they were also used almost exclusively on boat trains to Harwich and on the one through train in each direction between Lowestoft and London down the East Suffolk line.

Today they are mainly used as a freight locomotive, but as well as the Wherry line services they are also used on some passenger trains in Wales - and are very popular for enthusiasts specials.

They are owned by a number of different freight operators and each owner tends to put them in their own livery. The locomotives used on the Wherry Lines are hired from Direct Rail Services.

As well as those still working on Network Rail tracks, 34 Class 37s have been bought by enthusiasts for use on preserved railways where they are popular with diesel fans - and also as a reserve if a steam locomotive fails.

The North Norfolk Railway, the Mid Norfolk Railway, and the Epping Ongar Railway in this region all have Class 37s based on their line.

These lines usually paint them in 1960s BR Brunswick Green with yellow warning panels or 1970s BR Blue with yellow fronts.

One oddity about the class is that a small number have been "de-preserved." Locomotives bought by enthusiasts have been bought back or leased back by commercial rail companies to put back on the main line.

It seems certain that while their regular passenger duties in East Anglia may be coming to an end, there is still a long future ahead for the Class 37 diesel locomotive.

One colleague asked me: "Are they the noisy, smelly engines that you see at the side of Norwich station?" As I pointed out some might say that - but to many they are a superb example of 20th century engineering still doing the job they were designed for after the best part of 60 years!