Philip, 99, underwent a successful procedure for a pre-existing heart condition at St Bartholomew’s Hospital in the City of London on Wednesday – just three months before his 100th birthday.
The Palace said in a statement: “Following the Duke of Edinburgh’s successful procedure at St Bartholomew’s Hospital on Wednesday, His Royal Highness has been transferred to King Edward VII’s Hospital this morning.
“The Duke is expected to remain in hospital for continuing treatment for a number of days.”
The duke, the nation’s longest-serving consort, has spent 17 nights hospital – his longest ever stay.
He was initially admitted to King Edward VII’s – the royal family’s favoured hospital – in central London on February 16 after feeling unwell at Windsor Castle, before being moved by ambulance to St Bartholomew’s on Monday.
Concern will be heightened for the duke because of his advanced age, with the Duchess of Cornwall saying this week that Philip was “slightly improving” and adding: “We’ll keep our fingers crossed.”
The news was announced amid growing tensions within the royal family ahead of the Duke and Duchess of Sussex’s controversial televised Oprah interview.
The Sussexes have faced calls for the broadcast on Sunday to be postponed out of respect for Philip.
Buckingham Palace meanwhile has begun an investigation into allegations which surfaced in The Times that Meghan drove out two personal assistants and “humiliated” staff, leaving them in tears, which she denies.