ScotRail has defended its decision to introduce 40-year-old high speed trains as it emerged one of the locomotives due to join their fleet caught fire in Devon.

The fire broke out just hours before the ScotRail Alliance unveiled the first of 26 Intercity 125 high speed trains which are due to join their fleet next year.

The fleet, which is currently owned by Great Western Rail, will undergo a multi-million pound refurbishment to improve services, capacity and journey times.

One of the high speed trains, which were built in the late 1970s and early 1980s, caught fire at a depot in Exeter, Devon around 5am on Thursday.

The train was empty at the time of the blaze, which broke out in the engine compartment.

It is understood the train which caught fire was not yet in ScotRail's ownership and was due to arrive north of the border next year. Its damage is currently being assessed.

Later, ScotRail's managing director Alex Hynes and transport minister Humza Yousaf unveiled the trains' new ScotRail livery as the first locomotive arrived in Aberdeen for driver training.

A spokesman said: "The fully refurbished high-speed trains will deliver a true intercity service for Scotland.

"The arrival of the first train in Aberdeen is an exciting milestone as we build the best railway Scotland's ever had."

A Great Western Railway spokesman said: "As the train was out of service at the time, no customers or staff were affected."

The trains were due to undergo a multi-million pound upgrade, which would deliver more seats and luggage space.

Mr Hynes said the trains would be substantially refurbished before they entered service in Scotland.

He said: "(The high speed train) remains today the fastest diesel train in the world and customers love them.

"They will be far better than the existing trains, faster journeys, more seats, more services and a very high quality level of comfort."

Mr Yousaf said: "It is great to see this train arrive in Scotland for driver training, an important step towards delivery.

"Next year sees the start of a transformed inter-city service - connecting Scotland's seven cities with high-speed trains.

"The refurbishment programme has already started.

"And when the 26 fully upgraded trains roll out across the country, I know they will be popular with passengers: more seats, better journeys, the latest standard of comfort, better accessibility, and enhanced catering."