A London museum charting the religious, military and medical history of the Order of St John is to undergo a major refurbishment after receiving a £1.5m grant from the Heritage Lottery Fund (HLF).

Plans for the revamp of the Museum of the Order in St John in Clerkenwell include the creation of a new entrance area, increased exhibition space and upgraded galleries to provide an improved visitor experience. The scheme, called Open Gate, also includes the creation of a new learning space and exhibition area in the Grade I-listed Priory Church, which is one of three listed buildings within the site.

In addition, a collections research centre and a 'Pavement Museum' will be established to link the different parts of the museum, which is also housed in the Grade I-listed, 505-year-old St John's Gate building and an adjoining Grade II-listed building designed by architect Norman Shaw. It is hoped that the scheme will bring the history of the Order of St John to a wider audience, with artefacts documenting the story of the organisation from its inception in 1070, its role during the Crusades, and its current work through St John Ambulance.

Sue Bowers, head of HLF London, said: "The Order of St John has a fascinating tale to tell and this project provides it with the opportunity to engage many more people, especially children, in this extraordinary story." Alan Borg, Priory Librarian at the museum added: "The Museum of the Order of St John is one of the great hidden treasures of London, tracing the continuous history of a charity that dates back over 900 years.

"Thanks to the HLF, we are now going to 'Open the Gate' where all can see our amazing historical collections and follow the story of St John Ambulance up to the present day."