Factfile: InterCity 225

When authorisation to electrify the East Coast Main Line was given in the early 1980s, BR initially expected to build a fleet of production APTs (Advanced Passenger Trains) for the route.

However, after the cancellation of that project in 1983, other options had to be considered.

An electric variant of the InterCity 125 and a six-axle mixed traffic locomotive were mooted, but the latter never progressed beyond a single prototype (89001) and the focus soon switched to a lighter, high-power Bo-Bo known as ‘Electra’.

The design featured a novel arrangement derived from the Class 370 APT power cars, with traction motors mounted inside the body to reduce the unsprung mass, driving all four axles via separate cardan shafts and gearboxes.

This was expected to overcome the damage to track caused by the Class 81-87 electrics on the West Coast Main Line.

In 1986, the contract to build 31 ‘Electras’ was awarded to GEC, which sub-contracted the mechanical and construction elements to British Rail Engineering Ltd (BREL) at Crewe Works.

An initial batch of ten locomotives was introduced ahead of the full fleet, allowing extensive testing to take place as well as a brief period of passenger operation with Class 91s replacing one power car of several HST sets. With both the 6,480hp electric and 2,250hp Class 43 powering, the performance of these hybrid sets was best described as ‘lively’.

A total of 314 Mk 4 vehicles was built by Metro-Cammell at Washwood Heath in Birmingham between 1989 and 1992. Bodyshells were fabricated by BREL and Breda in Italy.

The fleet, formed into 30 sets, included 31 Driving Van Trailers to allow push-pull operation with the ‘91s’.

Controversially at the time, BR elected to buy Swiss-built SIG bogies for the Mk 4s, as it was believed these would perform better at higher speeds than the BR-designed T4 bogies.

However, complaints quickly surfaced about the ride quality of the SIG BT41 bogies, which was only cured by the fitting of additional dampers to the bogies and couplers.

Other innovations included passengeroperated plug doors, controlled emission toilets, and fully sealed gangways.

The exceptional crashworthiness of the Mk 4 design was cited as a factor in minimising the loss of life in the Hatfield (2000) and Great Heck (2001) accidents.

The IC225 fleet entered service in March 1989 and dominated East Coast Main Line operations between London, Yorkshire, Newcastle and Scotland until the delivery of the IETs in 2019-20.

Designed for a maximum speed of 140mph (225kph, hence the IC225 designation) and the installation of tilt equipment on the Mk 4 vehicles, the full potential of the fleet was never realised.

However, a shortened set powered by 91010 (now 91110) set the British railway speed record during a test run in 1989, reaching 161.7mph on the descent from Stoke Summit towards Peterborough.

Although APT-P and Eurostar Class 373⁄374s have run faster, 91110 still holds the title of Britain’s fastest locomotive.