This is why the Royal Train was seen in Yorkshire this week

Yet members of the Royal Family weren't aboard and the DB Cargo-owned diesel locomotive was not hauling any carriages.

The unit, 67005 Queen's Messenger, is one of two designated to work the Royal Train when it is required by the Queen or other senior royals.

The locomotive was being used for driver training purposes by DB Cargo ahead of a new freight route beginning between Hull Docks and the East Midlands Gateway container port.

When not part of the Royal Train, the two diesels are available for regular freight workings. They also often act as the 'Thunderbird' rescue locomotive, which is on standby to haul trains which have broken down.

The permanent Royal Train consists only of nine specially-fitted sleeper, dining and lounge carriages owned by Network Rail, and locomotives are supplied by DB Cargo on request. Prior to 1977, individual railway companies kept their own carriages for VIP use. The coaches date from 1977-87 and are stored at the Wolverton Works depot near Milton Keynes when not in use.

Only the Queen and Prince Charles can command use of the Royal Train, although it has sometimes been use to transport other VIPs, such as heads of state.

The drivers of the Royal Train are selected based on their skills, including whether they can stop within six inches of a designated position.

The two Class 67 diesels currently used to operate the train went into service in 2003, and are painted in the claret livery of the royal household. They are named Queen's Messenger and Royal Sovereign. Another unit, Diamond Jubilee, was allocated for occasional royal duties in 2012.

Steam locomotives have been used to haul the Royal Train on special occasions, such as in 2005 when the preserved Duchess of Sutherland pulled the carriages over the Settle to Carlisle line carrying Prince Charles.

Use of the Royal Train has declined in recent years for economical reasons, and members of the Royal Family often travel on scheduled services instead.