Image caption Mr Modi (centre) has been instrumental in pushing for the establishment of World Yoga Day

Today wasn't World Yoga Day but World Modi Day, sniped some critics this morning.

They said the Indian prime minister stole the show when he rolled out his yoga mat and eased uncomfortably into the lotus position to help break the world record for what is claimed to be the largest yoga session in history.

Narendra Modi boasts that he does yoga for an hour every morning but he looked a little stiff as he joined 37,000 other people to perform a series of asanas - yoga positions - on the lawns outside the Indian parliament in celebration of the first UN World Yoga Day.

Mr Modi had consistently said he wouldn't be taking part in the record attempt but in the event he stretched and puffed his way through the 35-minute routine with the rest of them.

Some say he simply couldn't resist the opportunity for an image that will undoubtedly appear in newspapers around the world tomorrow morning.

And that's in keeping with the real spirit of this event, because this is all about public relations.

Image copyright AFP Image caption Yoga sessions have been taking place to mark the day across India - and the world

The Indian government's new-found enthusiasm for yoga can be traced directly back to Mr Modi. He's already created a ministry of yoga with its own dedicated yoga minister, and his personal intervention is said to have been decisive in persuading the UN to designate June 21st as World Yoga Day.

The official publicity presents today's festivities as a humble celebration of an ancient Indian tradition of exercise. It is India's second greatest gift to the world after the number zero, according to Mr Modi's PR machine. But there was always much more to the government's agenda than that.

It isn't about propagating Hindu nationalism, as some in India's Muslim minority complained. The government quickly stripped out anything that could be described as "Hindu" from today's event in response to these criticisms, purging the Om chant and sun salutations from the menu.

But Mr Modi has recognised that yoga can do more for India than just encourage health and happiness through regular exercise.

Image copyright AP Image caption Mr Modi is hoping the event will boost India's image abroad - and perhaps his own at the same time

The Indian prime minister has always had a talent for publicity and he has spotted that with yoga India has a unique "brand" that can deliver huge economic benefits for the country.

According to one estimate the worldwide yoga industry has boomed into a $30 billion-plus business. Hundreds of thousands of tourists visit ashrams and undertake yoga classes in India every year. Mr Modi is hoping tens of thousands more can be persuaded to come.

But he's also got an eye on the country's wider image abroad. He sees yoga as a wonderful way to promote India in the world. What better badge of nationhood than this ancient tradition of health and harmony?

And if that enhances the image of Mr Modi himself along the way, all the better, will be Mr Modi's likely judgement.