United Kingdom, June 3 -- Princess Diana's hopes for a closer relationship between Prince William and Prince Harry have been revealed in a previously unseen letter.

Written less than two years before her death, it shows the late Princess of Wales - who died aged 36 in a Paris car crash in 1997 - expressing her desire to teach her sons "the importance of communication on a deeper level".

The handwritten correspondence, dated November 1995, was sent by Diana to royal supporter Michael Barratt after he wrote to her following her landmark BBC Panorama interview.

The two-page letter is now being offered for sale by Reeman Dansie's Royalty, Antiques and Fine Art auction, accompanied by its original envelope bearing Diana's handwritten name a...