The Government spent almost £1,000 hand-delivering the Article 50 letter declaring the UK's intention to leave the EU to Brussels, it has been revealed.
Two civil servants travelled to the Belgian capital with the letter by Channel Tunnel train on return business-class tickets costing £491.50 each, said the Foreign Office.
The terms of Article 50 of the EU treaties state only that a country wishing to leave the EU is required to "notify the European Council of its intention", and it is understood that this could have been done by email.
However, it was decided that the historic letter would be handed over to European Council president Donald Tusk by UK permanent representative Sir Tim Barrow in person on March 29 2017.
In response to a Freedom of Information request, the UK Representation to the EU said that the cost of two Eurostar Business Premier tickets, including a £1.50 booking fee and £2.50 change fee, came to £985.50.
"There were no other quantifiable costs associated with their travel," said the response. "Meals were provided on the Eurostar and the two civil servants stayed overnight at the Residence.
"The letter was then delivered to the President of the European Council by Sir Tim Barrow as part of his duties as UK Permanent Representative to the European Union at no additional cost."
Business Premier is the most expensive passenger ticket offered on regular Eurostar services, with standard tickets typically retailing for around £89-£159 each way.
The company's website states that the ticket includes "hot meals designed by Raymond Blanc, served with champagne", along with spacious seats, use of an "exclusive" lounge, a taxi-booking service and the option of changes and cancellation free of charge.
Holders of Business Premier tickets can turn up at the gate up to 10 minutes before departure, rather than 45 minutes with standard tickets.