Britain's Prince Charles officially became a pensioner as he celebrated his 65th birthday on Thursday, another landmark in his patient wait for the grand role he was born to play. The heir apparent, Queen Elizabeth II's eldest son, will mark the occasion in India, where he is currently touring with his wife Camilla, the Duchess of Cornwall, before flying to the Sri Lankan capital Colombo in the evening. Charles is set to visit a museum and a synagogue in Cochin, in the southern Indian state of Kerala, where he will receive a traditional blessing. Following his arrival in Colombo, Charles will attend a reception at the city's British High Commission, where a spokesman for the prince said there was "likely to be some singing and maybe even a cake". The celebrations began last week when he was presented with a homemade chocolate cake, decorated with the number 65, by schoolchildren from Govindpuri, one of Delhi's largest slums. The prince and his wife on Wednesday enjoyed a rest day on their nine-day Indian tour, giving them time for private celebrations. The couple relaxed at a new-age health spa near Cochin, which boasts of being "paradise untouched by time". The five-star Kumarakom Lake Resort specialises in Ayurveda, a traditional therapy which derives from the country's Vedic culture. But the future king will be thrown into the limelight on Friday when he takes the queen's place at the Commonwealth heads of government summit in Colombo. The queen, 87, has only missed one such summit since coming to the throne in 1952, signalling an increase in the amount of power being handed to the prince. He will meet with Sri Lanka President Mahinda Rajapakse, who is under scrutiny by the international community over alleged war crimes committed by the country's military during their war against Tamil rebels. Charles is not expected to address the claims during his three-day visit, but British Prime Minister David Cameron on Wednesday promised to "shine a spotlight" on Sri Lanka's rights record. The prince is now entitled to a £110.15 ($176.70, 131 euros) per week state-pension, but will donate the fee to a charity for the elderly, in keeping with his role as a philanthropist. "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," he told Time magazine recently. Charles is set to be the oldest-ever person to ascend the British throne -- and with the queen still in apparently rude health, it could be some time yet. But royal expert Jonathan Dimbleby insisted that the prince was happy to wait. "You might think that... this will be an especially poignant day," he wrote in Thursday's Guardian. "After all, he has yet to realise his royal inheritance or his constitutional raison d'etre. But you would be wrong. "He has always known that he could become king 'this year, next year, sometime...'"