The collection comprises letters between Philip Larkin and Anthony Thwaite, including a letter from Larkin to Noel Hughes and one from George Astley to Anthony Thwaite, as well as postcards and miscellaneous items. The letters are written mainly from Hull, but also from London, Oxford, Isle of North Uist, King's Lynn, Isle of Mull, Leicester, Cumbria and Scotland.
The original deposit in May 1994 comprised mainly letters from Philip Larkin to Anthony Thwaite, with just a few letters from Anthony Thwaite included (dating from 1959 to 1961). The remaining letters from Anthony Thwaite (dating from 1966 to 1985), numbering around 80 items, were purchased in 2013 and are not yet catalogued.