The Prince of Wales celebrates his 65th birthday today – a milestone for the man who will one day be king of the UK.

He will be spending the day in India with his wife Camilla as they are currently on a nine-day tour of the country. Their visit has already taken them to the shores of the River Ganges in the north, New Delhi, Mumbai, Pune and the picturesque Kerala.

Tomorrow, the prince will host the Commonwealth Heads of Government Meeting (CHOGM) in Sri Lanka. It will be one of his most significant duties to date as a future monarch as he will be deputising for the Queen on the world stage.

Charles has been heir to the throne since he was three and today he officially becomes a pensioner.

Like thousands of others, he will be claiming his pension this year – but will be donating it to an unnamed charity which supports the elderly.

The prince is entitled to the state benefit because he paid National Insurance contributions while in the Navy in the 1970s and made voluntary contributions later.

A king-in-waiting for more than 60 years, he has carried out countless royal engagements over the decades, undertaking 480 in the UK and 112 overseas in 2012 alone.

The prince is the oldest heir to the throne for almost 300 years and the longest serving heir to the throne.

Charles recently told US magazine Time he wanted to make the most of his position.

“I’ve had this extraordinary feeling, for years and years, ever since I can remember really, of wanting

to heal and make things better,” he said.

“I feel more than anything else it’s my duty to worry about everybody and their lives in this country, to try and find a way of improving things if Ipossibly can.”

As well as being the patron of more than 400 charities, he has set up The Prince’s Charities, a group of not-for-profit organisations, which raise over £100 million a year. He also founded The Prince’s Trust youth charity.

The prince, who is known for his strong opinions, particularly on the environment, architecture and farming, has faced criticism in the past over his ‘black spider memos’ to ministers – the name given to the handwritten letters he penned to government ministers expressing his views.

In July this year, the Attorney General’s decision to block public disclosure of letters Charles wrote to ministers in 2004 and 2005 was upheld by three High Court judges.

It was a defeat for the Guardian newspaper which said it had been fighting an eight-year battle to shed more light “on the way the heir to the throne seeks to influence government ministers even though he holds no elected position’’.

To mark his 65th birthday, the prince has guest-edited a special edition of Country Life, highlighting his fears for the farming industry.

In the 1990s, Charles faced turmoil in his private life, played out on a public stage when he split from Diana, Princess of Wales, and anguish when Diana – mother to his sons William, now Duke of Cambridge, and Prince Harry – died in a car carsh

Charles expressed concerns that farming ranked as one of the least desirable careers for young people and that the average age of a British farmer is 58, and questioned why farmers have to act as a “buffer for the retailer and consumer against all the economic uncertainties of producing food”.

He added: “It cannot be right that a typical hill farmer earns just £12,600, with some surviving on as little as £8,000 a year, while the big retailers and their shareholders do so much better out of the deal, having taken none of the risk.”

In the 1990s, Charles faced turmoil in his private life, played out on a public stage when he split from Diana, Princess of Wales, and anguish when Diana – mother to sons William, now the Duke of Cambridge, and Prince Harry – died in a car crash. Now nearly two decades later, life is more settled for the future king who has been married to Camilla for eight years.

She was once derided as the “other woman” in Charles and Diana’s relationship, but has established herself as a senior member of the Royal Family, attending the state opening of Parliament and travelling with the Queen in her Diamond Jubilee carriage procession.

This year, he has also experienced the joy of welcoming his first grandchild, Prince George, into the world. The proud grandfather has spoken of how he and his wife were “overjoyed’’ at the birth of Prince George and “so thrilled’’ for William and the Duchess of Cambridge.