The huge clue that has left people convinced the Queen will abdicate this year

Bookmaker Coral has slashed its odd on the Queen leaving her role as the head of the Commonwealth during 2020.

Queen Elizabeth II, who is the longest serving monarch in British history, has already had a tough year when it comes to her family.

Her grandson, Prince Harry and his wife Meghan Markle quit senior royal life and relocated to Canada, plus there has been controversy surrounding her son Prince Andrew.

Now some fans believe this might mean she might not continue her role past 2020.

The odds on the Queen retired were slashed from 5-1 to 6-4.

The bookie has placed odds on Charles to take over at 1-5, while Prince William is at 3-1 to be the next King.

John Hill of Coral said, 'Many punters feel as though the Queen will step down from the throne in 2020 which has forced us to slash the odds on her abdicating.

'Prince Charles is the long odds-on favourite to be the next monarch, however, Prince William has proved popular in our betting to leapfrog his father on the ladder.'

It comes after Her Majesty called Meghan Markle and Prince Harry back to Britain for a final engagement before they cease to be official royals.

The Sussexes will stop formally representing the Crown from spring, but before this, the Queen has asked them to return to Britain for a key event.

HM has asked that the Duke and Duchess attend the annual Commonwealth Service at Westminster Abbey on March 9.

They will attend the service as president and vice-president of the Queen's Commonwealth Trust.

The Queen has She has reportedly told friends of Harry and Meghan's exit, 'If that’s what they want - if they want to go - we must let them go.'