During the founders' lifetimes the collection contributed illustrations to more than four hundred books, and has remained one of the most important resources for authors writing about history of the British theatre.
Mitchenson's obituarist in The Times wrote, "[They] would raid antique shops and second-hand bookshops in search of anything which carried a morsel of theatrical history.
Their biographer Rupert Rhymes writes: Over the years this tall Victorian terraced house … overflowed with an amazing treasure trove of playbills and books from seventeenth-century folios onwards, programmes, periodicals, gramophone records, playwrights' prompt scripts, drawings, designs, and china figurines of great actors and actresses in their most famous roles.
[1]John Gielgud commented in 1968, "Mander and Mitchenson are a strange freakish pair – no taste but enormous diligence, and they have a remarkable collection of materials of all kinds and are really dedicated collectors – middle aged, one rather dandified, the other with a broken nose, looking like a Shaw burglar".
[7] Noël Coward, who referred to them as "Gog and Magog",[8][n 1] and dubbed them "the truffle hounds of the theatre",[9] so trusted their theatrical judgment that he left instructions in his will that after his death his estate should take advice from them, together with Sheridan Morley, on the continuing use of his literary and dramatic works.
[10] Sybil Thorndike, who referred to Mander and Mitchenson as "my dear detectives", gave them gifts and financial donations, calling their collection "the profession's passport to posterity".
"[1] By the end of the 1970s it was clear that the collection required larger premises, and the eighteenth-century Beckenham Place Park was selected, with the aid of the local authority.
Mitchenson moved to Beckenham with the collection and lived there until his death in Orpington Hospital, London, on 7 October 1992, aged 81, from renal failure and prostatic hypertrophy.
Parker's successor, Freda Gaye, described the MMTC as "a veritable museum [which] contains engravings, paintings, souvenirs, photographs, china figures, files of programmes of the London and provincial theatres, and a library of several thousand books."
The Beckenham site proved financially unsustainable, and in 2001, after a brief period in temporary accommodation – a disused cricket pavilion in south London – the collection was moved to a new home as part of the Jerwood Library of the Performing Arts in Greenwich.
[16] Mander and Mitchenson contributed introductions to four volumes of Noël Coward's collected plays, and numerous articles and reviews to the Encyclopædia Britannica, Theatre Notebook and Books and Bookmen.