Up to five state-of-the-art CCTV cameras will be installed in each carriage, capable of recording high-resolution images from every angle.

A total of 2,000 cameras will see almost every First ScotRail train covered within two years.

The multi-million-pound system will be the most hi-tech on the rail network, with a total of 230 trains equipped - more than any other operator.

The move builds on Scotland's pre-eminence in station security, where more than half have CCTV cameras - the highest proportion in Britain.

First ScotRail's entire diesel fleet and almost all its electric trains will be covered.

Andy Mellors, First ScotRail's engineering director, said: "It is essential the travelling public can feel confident and secure. We were impressed with the high- quality images from the new digital technology."

Inspector John Clark, of the British Transport Police, said: "This further indicates First ScotRail's determination to ensure our railways are as safe as possible. This is a considerable investment in safety that I am sure will benefit the industry in Scotland.

"British Transport Police are committed to working closely with our industry partners in the prevention and detection of crime, and this will assist us greatly."