This handout photograph released by Taj Hotels India on November 14, 2013, shows a birthday cake featuring an image of Britain's Prince Charles on a 'bus pass' in Cochin.
Britain's Prince Charles turned 65 while travelling in India on Thursday with his staff teasing him with a cake in the shape of a free bus pass, which he can now claim as a pensioner.
The heir apparent, Queen Elizabeth II's eldest son, wraps up a nine-day trip to India on Thursday before heading to Sri Lanka to open a meeting of leaders from the Commonwealth bloc.
To mark his becoming a pensioner, Princes Charles' staff ordered the cake from his luxury hotel in the southern port city of Kochi in the shape of a bus pass, granted to the over 65s in Britain to give them unlimited free travel.
"HRH Prince Charles. Valid from 14 Nov 2013. Concessionary travel funded by HM Government with your local authority," it read, according to a photo provided by the hotel. "Happy 65th Birthday!"
With rain disrupting his schedule, Charles and his wife Camilla, the Duchess of Cornwall, visited an old Jewish area, a church and a former colonial palace in Kochi in southern Kerala state.
Following his arrival in Colombo, Charles will attend a reception at the city's British High Commission on Thursday night where a spokesman for the prince said there was "likely to be some singing and maybe even a cake".
In an interview with Britain's Daily Telegraph on Thursday, Camilla revealed that her husband "likes people giving him a cake" and enjoyed last year's celebrations in New Zealand "when everyone gave him a bit of a party".
But she added he was "hopeless" to buy presents for, explaining that he composes detailed lists "so you get it exactly right".
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 Indian trip, giving them time for private celebrations.
The couple relaxed at a health spa near Cochin, which boasts that it is "paradise untouched by time", after several nights spent in a five-star spa hotel in the Himalayas.
Following a low-key visit largely unremarked upon in the Indian media, 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.
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 from the international community over alleged war crimes committed by the country's military against ethnic 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.
As well as a bus pass, the prince is now entitled to a £110.15 ($176.70) per week state pension, but he will donate the money 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 good 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...'"