The 96-year-old royal - who retired from public life last year - underwent hip replacement surgery last month, prompting speculation he wouldn't be fit enough to attend the nuptials on May 19, but not only is he back on his feet, he has able to walk unaided without the help or crutches or a stick.
A source told The Sun newspaper: ''The Duke is already walking unaided. He has amazing willpower. When he sets his mind to something he gets on and does it.
''He has been walking up and down stairs several times in succession.
''He has also been charging across rooms at full speed. He even had to be told to slow down.''
Philip went under the knife on April 4 at King Edward VII Hospital in Central London to replace the joint and spent nine days on bed rest before being allowed to return home.
A spokesperson for Buckingham Palace said in a statement when he left hospital: ''His Royal Highness The Duke of Edinburgh left King Edward VII's Hospital at midday today following a hip replacement operation last week.
''The Duke will continue his recovery at Windsor. His Royal Highness would like to convey his appreciation for the messages of good wishes he has received.''
His release comes just a day after his daughter Princess Anne, 67, said he was on ''good form'' after she paid him a visit at the hospital.
Philip was admitted to hospital on April 3 ahead of the planned procedure the following day, having suffered pain in the joint for about a month beforehand.
A spokesperson said at the time: ''His Royal Highness The Duke of Edinburgh was admitted to King Edward VII Hospital in London this afternoon for planned surgery on his hip which will take place tomorrow.''
Philip's surgery came after he was forced to skip the Royal Maundy Service at Leicester Cathedral last month because of his crippling hip pain.
He was named in the order of service, but a palace spokesperson said: ''The order of service was printed some weeks ago when it was hoped the Duke would be able to take part. His Royal Highness has since decided not to attend.''