The newly appointed Duchess of Sussex will become the first royal of the younger generation (INCLUDING Kate Middleton, Prince William and Prince Harry) to ride on the royal train alongside Queen Elizabeth for an official outing.
The train has been dubbed a 'palace on wheels' and the features an office, sleeping quarters and dining areas.
The nine burgundy carriages currently in use date from the Queen’s Silver Jubilee of 1977. Those carriages replaced others that first came into service in 1941.
The train also provides accommodation for royal staff, railway staff and personal protection officers.
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Queen Elizabeth II works at her desk on the Royal Train in May of 2002.
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The train ride, which leaves tonight from London, will give Her Majesty and new granddaughter-in-law the perfect opportunity for some bonding time.
Brian Hoey, author of At Home With the Queen, writes: 'The train seems to be the one place where, when away from home, the Queen and her family can truly relax out of the public gaze.'
Queen Elizabeth II and Prince Philip leave Manchester by train, 24th May 1961.
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'It may not have quite the same romantic images as when Queen Victoria rolled in majestic style from Windsor to Balmoral, insisting that the driver never exceeded 30 miles an hour, but there remains some of the glamour of bygone days.'
Hoey adds, 'When jet travel has in most cases reduced the longest journeys to a single day, Prince Charles says he gains a lot of pleasure just looking out of the window at the countryside of Britain passing by.'