King Charles has left London and is back in Norfolk to recuperate after starting his cancer treatment.

The monarch was driven away from Clarence House this afternoon, the first time he had been seen in public since his diagnosis was announced on Monday.

Charles and the Queen were taken from their London residence to nearby Buckingham Palace, where they were believed to have been flown to Sandringham via helicopter.

At around 4.30pm a helicopter was seen landing at the Sandringham.

The King was seen on his Norfolk estate on Sunday morning as he headed to church, but travelled to the capital on Monday so he could start his cancer treatment.

READ MORE: Will we see the King at Sandringham Flower Show this year?

Before leaving London, Charles is understood to have been visited by the Duke of Sussex, who made a transatlantic trip to see his father following his diagnosis.

Harry arrived in London from California on Tuesday afternoon less than 24 hours after the shock news was announced by Buckingham Palace.

The brief reunion between Charles and his youngest son - who have had a troubled relationship in recent years - has raised hopes the pair could be reconciled.

The King, 75, who began treatment for the condition on Monday, has postponed all public-facing duties, but is continuing with behind-the-scenes work on his red boxes of state papers.