It is the first time the British Transport Pollice has recruited part-time volunteers on a national basis.

The BTP, which numbers around 2,100 officers, is responsible for the rail and London Underground networks.

After successful pilot schemes using special constables around Liverpool, Manchester and Crewe, the force is hoping to recruit 426 specials over the next four years.

It is hoped the part-time volunteers will be particularly useful for events such as football matches and concerts.

With BTP's budget being cut by nearly �1m in real terms this year, unpaid specials are seen as the only way of increasing the force's public visibility.