Prince Philip: Duke of Edinburgh 'is progressing according to plan' say doctors as he awaits a possible visit from the Queen on his birthday Prince Philip marked his 92nd birthday today at the London Clinic Had exploratory abdominal surgery on Friday and is progressing well Palace spokesman refuses to confirm when the Queen will pay visit Earl of Wessex visited London Clinic today and left with a smile and a wave David Cameron wishes Duke a 'very happy 92nd birthday' on Twitter King's Troop Royal Horse Artillery fired 41-gun salute to mark milestone By Vanessa Allen and Simon Tomlinson The Duke of Edinburgh was 'comfortable and in good spirits' as he celebrated his 92nd birthday in hospital today following an exploratory operation on his abdomen, Buckingham Palace said tonight. Philip, who was visited this afternoon by his son the Earl of Wessex, is said to be 'progressing according to plan' and will remain in hospital for up to two more weeks while he recovers. Prince Edward was the first member of the Royal Family to pay Philip a visit today at the London Clinic where he underwent the operation on Friday. Palace sources refuse to confirm when the Queen will pay her husband a visit. All's well! Prince Edward waves to onlookers as he leaves the London Clinic after visiting his father, the Duke of Edinburgh, to wish him a happy 92nd birthday while he recuperates from an abdominal operation Good son: Prince Edward arrives at the London Clinic to visit his father Prince Philip on his 92nd birthday Welcome party: A member of staff greeted the Earl as he stepped from the vehicle and she curtseyed to the royal before walking into the building with him In a short statement the Palace said: 'His Royal Highness The Duke of Edinburgh is progressing according to plans at this early stage. He is comfortable and in good spirits. 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. Edward described the Duke of Edinburgh as doing 'well' after he visited his father earlier today. The Earl's afternoon visit lasted 20 minutes and as he left the hospital he was asked by the waiting press how his father was and replied: 'Well, thank you'. Prince Edward arrived at the central London hospital in a Land Rover Discovery shortly after 3.30pm. A member of staff greeted the Earl as he stepped from the vehicle and she curtseyed to the royal before walking into the building with him. The police presence around the hospital increased ahead of Edward's arrival and broadcasters and photographers sprung into action to capture the moment. Bringing cheer: A man delivers flowers and birthday balloons to the London Clinic, where the Duke of Edinburgh is recuperating following an operation on his abdomen 'Doing well': The Duke was admitted to the London Clinic for the pre-arranged operation on Thursday evening, following a garden party at the Palace that day Following the Duke's operation on Friday, Buckingham Palace said he was 'progressing satisfactorily' and was 'comfortable', but has not released any further updates. Edward's visit indicates the Duke is well enough to see callers but he did not stay long, leaving after 20 minutes. The Duke has already received the good wishes of the Prime Minister on his birthday and gun salutes have been fired across the UK to mark the milestone. Prince Philip, pictured last week before his operation, marked his 92nd birthday in hospital today Earlier, there was speculation the Queen may be the first person to visit her husband, but she has not yet been seen at the hospital. Prince Philip has so far been too tired to accept visits, but if his doctor gives the OK, the Queen may visit soon after returning from her weekend break at Windsor Castle. Prince Charles and Camilla were at Birkhall, their private residence at Balmoral. A source told The Daily Telegraph: 'Nothing has been decided yet about visitors. 'The golden rule where the Queen is concerned is that she doesn't want to disrupt the work of the hospital at all, so she will be guided by the doctors looking after the Duke.' The Duke received the good wishes of David Cameron today as gun salutes were fired to mark his milestone. In the hours following the procedure, Buckingham Palace said the Duke was 'progressing satisfactorily' and that he was 'comfortable', but did not released any further updates until this evening. David Cameron took to Twitter to send a birthday message to the Duke who has so far not received any royal visitors. He wrote: 'Wishing the Duke of Edinburgh a very happy 92nd birthday as he recovers in hospital today.' The King's Troop Royal Horse Artillery fired a 41-gun royal salute at noon to mark Philip's birthday. The Duke was then admitted to the London Clinic ahead of Friday's pre-arranged operation on Thursday night, following a garden party at the Palace that day. Royal honour: King's Troop Royal Horse Artillery fire a 41-gun salute in Green Park to celebrate the 92nd birthday of Prince Philip, the Duke of Edinburgh in London today Marking milestone: The 41-gun salute took place in Green Park at noon, followed an hour later by a 62-round salute by the Honourable Artillery Company at the Tower of London The Duke has yet to receive a visit from the Queen at the London Clinic where he had an abdominal operation The surgery, known as a laparotomy, was performed on Friday under general anaesthetic. He was visited by the royal doctor, Professor John Cunningham, on Saturday and the results of the operation are expected later this week. The Duke is likely to remain in hospital for up to two weeks in total while he recovers.