The Queen is now the oldest monarch in the world after the death of King Abdullah of Saudi Arabia at the age of 90.

Her Majesty, who is 88, was born on April 21, 1926 and has reigned through more than five decades, celebrating her Diamond Jubilee in 2012. She took the throne at the age of 25.

But despite being the oldest monarch in the world - she is only the second longest-reigning.

King Rama IX of Thailand has served for 68 years whereas the Queen's reign is just under 63 years.

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The Queen is now the oldest monarch in the world after the death of King of Saudi Arabia Abdullah at the age of 90 (pictured together in 2007)

King Abdullah died in hospital last night aged 90 and was immediately replaced by his brother Prince Salman, 79.

His death will be upsetting for Her Majesty and her family, having built a close relationship with him.

Death: Saudi Arabia's King Abdullah bin Abdulaziz died following a battle with pneumonia

He was taken to hospital on New Year’s Eve with suspected pneumonia, is believed to have left four wives and 22 children after nearly ten years on the throne of one of the world’s richest countries.

It is likely that Prince Charles – a personal friend of King Abdullah – will attend his funeral today.

Either the Queen will make the Royal Flight available to Charles or a private jet will be chartered.

King Abdullah was one of the 37 sons of King Abdul Aziz Al-Saud, who created the modern state of Saudi Arabia in 1932.

His brother Prince Salman, 79, is already king but there were concerns last night that, despite the swift succession, the news would send shockwaves across the Middle East.

Saudi Arabia is already facing uncertainty over the recent dip in global oil prices and the rise of terror group Islamic State in neighbouring Iraq.

The price of crude oil rose by two per cent on the world markets after the king’s death was announced.

The Prime Minister has paid tribute to his work for peace in the region.

Friends: Prince Charles and King Abdullah were personal friends. The Prince of Wales is expected to attend his funeral today

The new King Salman, pictured arriving in Tokyo in 2014, is taking over as monarch at the age of 79

David Cameron, who visited Saudi Arabia in 2012, said: 'I am deeply saddened to hear of the death of the Custodian of the Two Holy Mosques, His Majesty King Abdullah bin Abd Al Aziz Al Saud.

THE WORLD'S OLDEST MONARCHS Queen Elizabeth II: 88 years, 277 days King Abdul Halim Kedah of Malaysia: 87 years, 56 days King Rama IX of Thailand: 87 years, 49 days King Sabah Al-Ahmad Al-Jaber Al-Sabah of Kuwait: 85 years, 221 days King Humaid bin Rashid Al Nuaimi Ajman of United Arab Emirates: 84 years, 22 day Advertisement

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'He will be remembered for his long years of service to the Kingdom, for his commitment to peace and for strengthening understanding between faiths.

'My thoughts and prayers are with the Saudi Royal Family and the people of the Kingdom at this sad time.

'I sincerely hope that the long and deep ties between our two Kingdoms will continue and that we can continue to work together to strengthen peace and prosperity in the world.'