JD Salinger was regarded as a recluse for much of the last 50 years of his life but previously unseen letters written by the author to a friend in Britain show that while he may have shunned the limelight, he enjoyed a simpler life of gardening, eating hamburgers and following the tennis career of Tim Henman.

50 letters and four postcards, written by Salinger to Donald Hartog a Londoner whom he met in 1938, reveal that at a time when the Catcher in the Rye author was widely believed to be a near-hermit he was actually enjoying group bus trips to Niagara Falls and regularly indulging a passion for the theatre.

The letters were donated to the University of East Anglia by Hartog's daughter, Frances, after her father died in 2007, and the university has made them publicly available on the first anniversary of Salinger's death.

"Salinger had this reputation as a recluse, that he kept himself to himself," said Chris Bigsby, professor of American studies. "This is another Salinger, this is an ordinary Salinger, not the reclusive, angry person people thought he was."

The letters reveal the author enjoyed listening to the Three Tenors – Jose Carreras was his favourite – and particularly liked watching tennis, with Salinger disclosing a particular fondness for "Tiger" Tim Henman.

Salinger also told Hartog that he thought Burger King hamburgers were better than those from other chains, while he described trips to the Niagra Falls and the Grand Canyon.

The letters are not the only surviving correspondence by Salinger, but they cover a period late in his life when he was at his most elusive.

Hartog and Salinger met as teenagers in Vienna, sent there by their families to learn German.

They kept up their correspondence through the second world war. Salinger travelled to Britain in 1989 for Hartog's 70th birthday.