The queen, or a member of her staff, purchased a first class ticket for 47.20 pounds (about $75), Cambridge First reported. The operator of the First Class Connect service said the only royal perk was that the queen got a compartment to herself.
While Elizabeth has a private train, she has made the 100-mile journey by public conveyance at least twice before. The queen boarded the train Tuesday at King's Cross Station, the same station the fictional Harry Potter uses to travel to Hogwarts School of Witchcraft and Wizardry.
The royal family spends the Christmas season at Sandringham House, an estate in Norfolk bought by Queen Victoria for her son, the future King Edward VII. This year, after the weddings of two of the queen's grandchildren, an unusually large group is expected.
The Daily Telegraph reported Monday space is so short the son and daughter of the late Princess Margaret and their families have been assigned to a corridor that normally houses servants. The servants are having to double up.
The queen wore one of her trademark headscarves and carried a handbag as she left the train at King's Lynn, escorted by royal protection officers. She was met by a caravan of Land Rovers.
Most of the other passengers on the 10:45 train did not know they were traveling with royalty, Cambridge News said.