Britain's Kate, Duchess of Cambridge, right, accompanies Queen Elizabeth II, left, and Prince Philip as they arrive at Baker Street underground station in London for a visit to mark the 150th anniversary of the London Underground, March 20, 2013.
Kate, Duchess of Cambridge, accompanies Queen Elizabeth II and Prince Philip, not pictured, to Baker Street underground station in London for a visit to mark the 150th anniversary of the London Underground on March 20, 2013.
Kate, Duchess of Cambridge, makes an official visit to Baker Street underground station on March 20, 2013, in London.
Queen Elizabeth ll and Prince Philip, Duke of Edinburgh, make an official visit to Baker Street underground station on March 20, 2013, in London.
Kate, Duchess of Cambridge, makes an official visit to Baker Street underground station on March 20, 2013, in London.
Kate, Duchess of Cambridge, center, receives flowers at Baker Street underground station in London during a visit to mark the 150th anniversary of the London Underground on March 20, 2013.
Queen Elizabeth II walks through a ticket barrier as she makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Kate, Duchess of Cambridge, walks through a ticket barrier as she makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Queen Elizabeth II makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Queen Elizabeth II smiles as she makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Kate, Duchess of Cambridge, makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
A badge, similar to the one given to Kate, Duchess of Cambridge, is displayed as she makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Kate, Duchess of Cambridge, right, stands with Prince Philip as Queen Elizabeth II, not pictured, unveils a plaque at Baker Street underground station in London for a visit to mark the 150th anniversary of the London Underground on March 20, 2013.
Kate, Duchess of Cambridge, watches as Britain's Queen Elizabeth II unveils a plaque at Baker Street underground station in London for a visit to mark the 150th anniversary of the London Underground on March 20, 2013.
Queen Elizabeth II walks through the carriage of a parked train she was shown around at Baker Street underground station in London for a visit to mark the 150th anniversary of the London Underground, March 20, 2013.
Queen Elizabeth II walks through the carriage of a parked train she was shown around at Baker Street underground station in London for a visit to mark the 150th anniversary of the London Underground, March 20, 2013.
Queen Elizabeth II stands in a drivers' cabin as she makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Kate, Duchess of Cambridge, is shown round the carriage of a parked train at Baker Street underground station in London for a visit to mark the 150th anniversary of the London Underground, March 20, 2013.
Prince Philip, Duke of Edinburgh, makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Queen Elizabeth II makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Queen Elizabeth II inspects a vintage train as she makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Kate, Duchess of Cambridge, makes an official visit to Baker Street underground station to mark 150th anniversary of the London Underground on March 20, 2013, in London.
Queen Elizabeth II makes an official visit to Baker Street underground station on March 20, 2013, in London.