The Prince of Wales will be joined by his sister the Princess Royal for what is expected to be his first official public engagement since his Covid isolation.

The pair will present The Queen’s Anniversary Prizes for higher and further education in a ceremony at St James’s Palace on Thursday.

Charles, who was forced to pull out of engagements in Winchester last week after again testing positive for Covid-19, is then due to visit Wales on Friday.

The engagements come in the wake of a Metropolitan Police investigation being launched into the alleged cash-for-honours scandal involving the heir to the throne’s Prince’s Foundation charity.

The pressure group Republic contacted Scotland Yard last September and reported both the future king and Michael Fawcett, Charles’s former royal valet, on suspicion of breaching the Honours (Prevention of Abuses) Act 1925.

At the time Clarence House said the prince had “no knowledge” of the alleged cash-for-honours scandal.

Mr Fawcett, who has since resigned as chief executive of the foundation, was accused of promising to help secure a knighthood and British citizenship for a Saudi billionaire donor.

It was announced on February 10 that Charles, who first fell ill with coronavirus in 2020, had received a positive test result.

Under the current rules, people can leave isolation after five full days, if they test negative on days five and six.

Prime Minister Boris Johnson has signalled that laws requiring people in England with Covid-19 to self-isolate will be lifted within weeks, meaning Charles just missed out on any changes.

The Duchess of Cornwall carried out a string of engagements on the day Charles tested positive, describing herself as “luckily” negative the same day.

But on Monday it was revealed that she too had tested positive and Clarence House alerted the organisations Camilla had visited and the media who covered her engagements.

Concern had been growing for the Queen’s health after it was confirmed she met with Charles two days before he tested positive for the virus.

Buckingham Palace has continued to refuse to confirm whether the Queen had tested positive or negative for Covid, citing medical privacy, and saying last week only that she was not displaying any symptoms.

The monarch carried out virtual audiences with ambassadors from Windsor Castle on Tuesday, and held an in-person audience with military staff on Wednesday, which appeared to suggest she may have escaped the virus.

On Thursday, Charles and Anne will present medals and scrolls to prize winners and meet guests at an educational awards event in London.

On Friday, Charles is due to meet staff and patients at St David’s Hospice in Newport, before visiting Dylan Thomas Community School in Swansea which runs the Prince’s Trust’s Achieve programme.