Prince Edward, the couple's youngest son, also went to the hospital, the Daily Express reported.
Philip, the Duke of Edinburgh, had exploratory surgery Friday. He is expected to avoid public appearances for the next two months followed by another two months of recuperation at Balmoral, the royal family's Scottish retreat.
Buckingham Palace issued an optimistic statement Monday: "His Royal Highness the Duke of Edinburgh is progressing according to plans at this early stage. He is comfortable and in good spirits."
Prince Edward was asked as he left the London Clinic about his father's condition and responded, "Well, thank you."
The queen brought a birthday card for her husband.
Philip's birthday was marked by two gun salutes in London and others elsewhere. The King's Troop Royal Horse Artillery fired a 41-gun salute in Green Park and the Honorable Artillery Company an even larger salute at the Tower of London.
Philip announced when he hit 90 that he was cutting back on his public duties although he continues to make many appearances with his wife and on his own. The queen, now 87, maintains a heavy schedule but has handed off some responsibilities to her children.
Notable deaths of 2014 [PHOTOS]