It is named after Montagu C. Butler author of a number of works including Step by Step in Esperanto and the comprehensive Esperanto-English Dictionary.
It is housed in purpose-built premises at the offices of the Esperanto Association of Britain which are now located at the Wedgwood Memorial College, Barlaston, Stoke-on-Trent, Staffordshire, having moved from Holland Park, London in April 2001 due to financial pressures.
For details of other major collections consult Esperanto library.