Prince Philip is showing signs of improvement more than three weeks after he was admitted to hospital but is in some pain, according to Prince Charles’ wife Camilla.

The 99-year-old husband of the Queen, who has also undergone tests for a pre-existing heart condition, “hurts at moments”, the Duchess of Cornwall said.

Philip, the Duke of Edinburgh, was admitted to hospital on February 16 after he felt unwell to receive treatment for an unspecified but not coronavirus-related infection.

On Monday, he was transferred to another hospital which specialises in cardiac treatment for additional tests and observation relating a pre-existing heart condition, Buckingham Palace said.

On a tour of a vaccination centre in south London, Camilla, the wife of heir-to-the-throne Prince Charles, told a volunteer the Duke was “slightly improving” but it “hurts at moments”.

“We keep our fingers crossed,” Camilla told the volunteer at the centre in Croydon.

Greek-born Philip, who turns 100 in June, has required hospital treatment a number of times in the last decade for a recurrence of a bladder infection.

At Christmas in 2011 he had an operation to clear a blocked artery in his heart after being rushed to hospital with chest pains.

His current stay is the longest he has required hospital treatment, although Buckingham Palace has said he is comfortable and in good spirits.

The Queen, 94, has remained at Windsor Castle, west of London, where the couple have been staying during the coronavirus lockdown and has continued to carry out her official duties, albeit remotely.

Both she and Philip have received their first COVID-19 vaccine dose as part of the UK’s mass vaccination rollout.

Meanwhile, Buckingham Palace said it was “very concerned” about a newspaper report in The Times in which former staff allege bullying by the Duchess of Sussex.

There has long been speculation about the atmosphere in the Sussex household after a number of staff left, and the newspaper chronicles what it describes as “turmoil” within palace walls.

“Accordingly our HR team will look into the circumstances outlined in the article,” Buckingham Palace said in a statement on Wednesday.

“Members of staff involved at the time, including those who have left the Household, will be invited to participate to see if lessons can be learned.”

The Royal Household will not tolerate bullying or harassment in the workplace, it added.

Prince Harry and his wife, Meghan, have hit back at what they say is a “smear campaign”  ahead of their tell-all interview with Oprah Winfrey on March 7.

Harry and Meghan’s lawyers responded on Wednesday saying “we are disappointed to see this defamatory portrayal of the Duchess of Sussex given credibility by a media outlet”.

“It’s no coincidence that distorted several-year-old accusations aimed at undermining the Duchess are being briefed to the British media shortly before she and the Duke are due to speak openly and honestly about their experience of recent years,” the statement read.

“The Duchess is saddened by this latest attack on her character, particularly as someone who has been the target of bullying herself and is deeply committed to supporting those who have experienced pain and trauma.

“She is determined to continue her work building compassion around the world and will keep striving to set an example for doing what is right and doing what is good.”

-with AAP