The Queen will carry out her first public engagement in more than a week on Wednesday when she joins the Duchess of Cambridge at an event celebrating the 150th anniversary of the Tube.
The Queen and Duke of Edinburgh will travel with Kate to Baker Street Underground station in London to mark the transport network's milestone.
Duchess Kate arrived at Baker St Tube station on Wednesday morning
The Queen, who had been suffering symptoms of gastroenteritis, has been carrying out her duties within Buckingham Palace but last week cancelled a trip to London's East End to visit Tech City.
The Duke of York, who carried out the engagement without his mother, said she was "not ill" but stayed at home as precaution.
The Queen's last visit to the underground was in 2010
The last time she was seen at an official event was an engagement last Monday evening when she signed the Commonwealth's new charter.
The Queen last visited a Tube station in February 2010, when she travelled to Aldgate station to meet staff and view a memorial plaque dedicated to the seven people killed at Aldgate during the July 7, 2005 bombings.
During the royal party's visit to Baker Street, they will meet station staff in the ticket hall before moving downstairs to the platform where maintenance and train workers will be waiting.
The Queen, Philip and Kate will also view a restored 1892 carriage and meet staff and apprentices involved in the restoration of the rolling stock.
They will then walk through a new S7 train before she unveils a plaque, naming the train Queen Elizabeth II.
The royal party will also meet staff from the Railway Children charity, an international organisation which works to help homeless youngsters.