A huge archive of previously unseen letters and memorabilia from Mahatma Gandhi's life have been secured in a private deal, just a few days before they were due to sell at Sotheby's on July 10.

The archive consists of thousands of unseen documents and letters

The archive was reportedly bought for £700,000, after a report from a group of historians urged the Indian government to purchase them. The historians had recently been to London to examine the collection and found them to be of considerable significance, though matters were complicated by the fact that the government is not usually allowed to participate in auctions.

The letters were consigned from the personal correspondence of Hermann Kallenbach, a German bodybuilder who became very close friends with Gandhi following his visit to South Africa in 1904. The selection contains four decades of correspondence between the pair from 1905-1945, the majority of which has never been published.

The Indian government had previously tried to purchase the letters directly from Kallenbach's family, but was not able to meet the price they demanded at the time. It is believed that the fresh decision to negotiate the sale was spurred by a recent book which describes the pair's relationship as "the most intimate, also ambigious", that was banned in Gandhi's home state of Gujarat last year.

With the booming Indian economy creating a new influx of wealthy collectors and investors, there is an increasing desire to return the nation's lost artefacts to home soil. The current situation is reminiscent of another sale in April this year, when blood-soaked soil from Gandhi's assassination site was bought by Indian politician Komal Morarka, who said it would be returned to India to be displayed as an item of national importance in a Mumbai museum.