The Queen visited her husband Prince Philip on Monday evening, personally delivering a birthday card as he turned 92.
Smiling cheerfully as she entered the London Clinic, Her Majesty wore an off-white suit with pearl necklace and earrings, along with a brooch. In her hand she carried an envelope addressed to HRH The Duke of Edinburgh.
Prince Philip was "comfortable and in good spirits" as he received a visit from his wife at 7pm.
"His Royal Highness The Duke of Edinburgh is progressing according to plans at this early stage," a statement from Buckingham Palace read on Monday.
"He will remain in hospital for up to two weeks, and it is expected he will then be taking a period of convalescence of approximately two months."
A pair of gun salutes were fired in the Prince's honour on his birthday in the capital's Green Park, Edinburgh Castle, the Tower of London, Cardiff Castle and Hillsborough Castle in Northern Ireland.
British Prime Minister David Cameron also sent him birthday wishes via Twitter. "Wishing the Duke of Edinburgh a very happy 92nd birthday as he recovers in hospital today" wrote the Prime Minister.
His son Prince Edward had gone to see his father earlier in the day. When asked how he was, The Earl of Wessex said "Well, thank you."
The Queen's husband underwent exploratory surgery on his abdomen at the London Clinic on Harley Street on Friday.
The Duke of Edinburgh was admitted to hospital for the scheduled procedure last Thursday following his attendance at the Queen's summer garden party at Buckingham Palace.
Prince Edward spent the weekend in Stockholm, Sweden with his wife Sophie, Countess of Wessex at Princess Madeleine and Chris O'Neill's picture-perfect wedding.
After the Duke's operation on Friday, Buckingham Palace said he was "progressing satisfactorily".
The results from the operation are being analysed, and his hospital stay is expected to last about two weeks.
His admission to hospital came after he missed an engagement a few days previously because he felt "under the weather".
"He is in very good health ," a Buckingham Palace spokesperson said. "He felt unwell on Monday and missed an engagement but that was down to the fact he had temporarily lost his voice."
Last summer, the 91-year-old spent five nights in hospital and missed some of the events for the Queen's Diamond Jubilee celebrations due to a recurring bladder infection.