LONDON, Oct. 6 -- China has not gone back on its agreements with Britain over the future of Hong Kong, whose autonomy is far greater than what Britain expected three decades ago, a former aide to late British Prime Minister Margaret Thatcher has said.

"Hong Kong has very extensive autonomy, far greater than we believed actually could be achieved when the Hong Kong joint declaration with China was negotiated," Charles Powell, former private secretary to Thatcher during the 1980s, told British BBC Radio 4's The World This Weekend on Sunday.

"They have far better conditions, including political conditions than any other city in China, but the bottom line is -- they are a city in China," said Powell, who was a key foreign policy advisor to Thatcher when Britain agreed to return Hong Kong to China.

He added that protesters in the Occupy Central movement in Hong Kong are "unrealistic."

"The position about elections has been clear since the basic law was published in 1990 and I don't believe for one moment the Chinese are going to change that basic position," he said.

"When Hong Kong was reintegrated into China, an agreement was made and implemented under Chinese law, which made very clear that there would be restrictions," recalled Powell, who was awarded a life peerage in 2000 and now sits in the British House of Lords.

Noting that Hong Kong has always been part of China, the veteran politician said Britain "rented it for a while" and did not introduce democracy in the territory.

Powell encouraged young people in Hong Kong to "make the most of" their existing autonomy and freedoms.

"If I was a young person in Hong Kong, I would focus on making the most of the very wide degree of freedom and autonomy, which I already have: making the most of the job opportunities in Hong Kong, the freedom to travel, the freedom to seek work abroad too, the prosperity of Hong Kong, the education available in Hong Kong... all of that, and enjoy," he said.