London, Jul 12 (IANS): A rare 1931 pencil portrait of Mahatma Gandhi and a collection of his handwritten letters that went under the hammer at the Sothebys auction here on Tuesday have been bought by noted Indian businessman Cyrus Poonawalla, popularly known as the 'vaccine billionaire'.

Poonawalla founded the Serum Institute of India in 1966, today one of the world's largest vaccine makers by volume, producing 1.3 billion doses annually.

Poonawalla bought the lot for 32,500 pounds (nearly Rs 27 lakh, saying he wanted to bring the historic and rare work back to India.

"I am absolutely delighted to have acquired this beautiful signed image and to have the opportunity to bring a work of such historical value back to India.

"Mahatma Gandhi is one of the most respected and revered figures in the world and considered to be the father of our nation, and so to have such a rare and intimate depiction of him at work, and signed by the great man himself, is an incredible honour and an absolute pleasure," Poonawalla said in a statement.

The pencil portrait was drawn by artist John Henry Amshewitz. It features Gandhi focused on writing something and is inscribed with the words "Truth is God/MK Gandhi/4.12.'31."

"Gandhi usually refused to sit for formal photographs, let alone a portrait, making this an extremely rare portrayal of the political leader at work," Sotheby's said in a statement.

Poonawalla has also bought a collection of Gandhi's handwritten letters addressed to Sarat Chandra Bose and his family.