Herbert Smith Freehills India practice chairman Chris Parsons will be walking 1260 km from the Gateway of India in Mumbai to Bangalore from January to February of 2015, aiming to cover a distance of 30 marathons in 30 days.

Hoping to raise $1m for the Loomba foundation which works for Indian widows and their children, Parson said it was his way of celebrating his 30 years with Herbert Smith Freehills, as it is now known.

The campaign, which kicked off earlier this week, has raised around $30,000 towards the target.

Parsons, who said he was now starting his six months of training for his walk, had in 2011 raised $200,000 for the Loomba Foundation by cycling from London to Gibraltar.

For this walk he said he has support from UK politicians Nick Clegg, entrepreneur Richard Branson, barrister Cherie Blair, the cricketer Chris Gayle and some corporate supporters such as Pepsi through Gatorade and Tata Consulting which is helping with logistics. Apollo Hospitals had committed to providing him with round-the-clock access to a physiotherapist, a doctor and a nutritionist.

He said that taking care of his feet would be a major challenge in the walk. “Your feet get wet through sweat, the skin gets very soft and it blisters very easily. Also [there’s] the challenge of walking between 10 and 12 hours a day and the mental bit: thinking, 15 days in, I’ve got another 15 to go.”

23 June was celebrated as International Widows Day, after the Loomba Foundation “successfully lobbied the UN and governments” to establish the day to throw light on the plight of 100 million widows worldwide.

• Campaign page