Less than six months after the last AL5 was accepted into traffic, the first of a new 'standard' design of AC electric locomotive was delivered. A fleet of 100 Class AL6 locomotives was built in time for the opening of the London extension of the West Coast Main Line electrification scheme. In theory, this standard fleet built on the best features of the prototype classes, but in reality, the AL6s brought problems of their own.
The resounding success of the electrification to London, plus political pressure from north of Weaver Junction saw plans emerge for an extension of the wires to Glasgow. This was eventually authorised and to meet the requirements for a more powerful loco capable of tackling the steep gradients of northern England and the Scottish Borders, the Class 87, was designed. Although this loco was a much-improved development of the AL6 (by now Class 86), only 36 were built, a result of Government restrictions on spending. The northern wires were energised in 1974, by which time the 87 fleet was waiting to take on the northern fells.
In 1979, with several years of electrification success behind them, British Rail unveiled the Class 370, Advanced Passenger Train (APT), designed to tilt and thus be able to take corners at up to 50% higher speeds than conventional trains. A fleet was envisaged for the West and East Coast Main Lines by the mid to late 1980s, replacing traditional loco hauled trains. The problems and pitfalls of the APT project, compounded by relentless media sensationalism, eventually caused BR to abandon the train, some say just as it was reaching its potential. A consequence of the lack of APT was that the 86s and 87s have remained in frontline WCML duties for an extra 15 years or so, only beginning to be replaced in the early 2000s by new - tilting - trains!
Sadly, the APT-based third generation of WCML electric traction never really came into being, and it was several years before a new "third generation" of AC traction appeared.