Prince Charles and Princess Anne team up for rare joint outing in London - best photos

The Prince of Wales, 73, stepped out with his sister, the Princess Royal, 71, for a rare joint engagement on Thursday. It marked the first time Prince Charles had been seen in public since his COVID-19 isolation.

The royal siblings presented The Queen's Anniversary Prizes for higher and further education in a ceremony at St James's Palace.

Charles, who was forced to pull out of engagements in Winchester last week after testing positive for COVID-19 for a second time, has also postponed his visit to Newport and Swansea on Friday due to Storm Eunice. 

READ: Prince Charles cancels royal outings due to 'dangers posed by Storm Eunice'

The Queen's Anniversary Prizes are awarded every two years to universities and colleges whose work has been judged to show excellence, innovation and impact in any field or discipline, and to be of benefit to society, as well as the institutions themselves. 

This year, 21 UK universities and colleges have been awarded Prizes, recognising a wide range of pioneering work, including the design and creation of a COVID-19 vaccine and efforts to deliver vitally important data modelling in response to the global pandemic. 

MORE: 10 sweet photos that show Princess Anne's close sibling bond with Prince Charles

The royal siblings looked delighted to be in one another's company upon arrival at the ceremony.

The Queen's eldest children are only two years apart in age and were only young when their mother became monarch.

As children, Charles and Anne kept one another company when the Queen and the Duke of Edinburgh carried out official engagements and overseas tours. 

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The first Queen’s Anniversary Prizes were awarded in 1994, and to date, a total of 296 prizes have been presented to 137 institutions - 83 universities and 54 colleges of further education. 

The Prize itself consists of a silver gilt medallion and a decorated and inscribed certificate granting the award, signed by the Queen. The Prizes scheme is managed by The Royal Anniversary Trust, an independent charity.

The Princess Royal meeting university representatives after the presentation. 

The Queen's only daughter looked elegent in a dark green button-up coat with one of her signature brooches. 

Charles and Anne often top the hardest working royals list, carrying out hundreds of engagements a year for their patronages and charities.