As India's capital baked in a heat wave, banker Gaurav Gupta sat down for lunch at a new air-conditioned restaurant, to be greeted by a smiling waiter who took his order for a traditional "thali" meal of flatbread, lentils, vegetables and rice.

Nothing unusual, except that the employee, like most of his colleagues, is a convicted murderer serving time in South Asia's largest prison complex.

"Tihar Food Court" in west Delhi, a rehabilitation effort kicked off by the Tihar prison, opened in the first week of July on an "experimental basis" while awaiting formal clearances. It is sited half a km (0.6 mile) away from prisoners' dormitories.

With a spacious interior lined with wooden tables and walls adorned with paintings done by prisoners, the 50-seat restaurant has been praised for the polite behaviour of its employees, who were trained by a prestigious nearby hotel management school.

"The food is average," said Gupta. "But the hygiene factor is really good, very clean. And it's a good thing they are employing prisoners." Restaurant manager Mohammad Asim said there are around 50 customers every day, with each worker paid 74 rupees for the day's work.

To be eligible to leave prison and work in the restaurant, inmates must have kept up an "unblemished record" through at least 12 years of imprisonment, besides a high school education.

Prisoners eligible to be released within two years are picked for the job, to minimise their temptation to escape. They travel to work by cycle or on foot, as authorities "trust them enough" not to need a security escort.

Customers had few qualms dealing with the Tihar prisoners.

"I think that Tihar authorities have observed them for years and have decided they can be placed in front of the public ... so I don't think there is a need to be worried," said first-time customer Atul Singh, who works with the Indian unit of South Korean electronics giant Samsung.