Assembly Rooms had their origins in the early 18th century. The earliest known reference to the Dedham Assembly Rooms in is in a letter of Horace Walpole who in 1748 referred to " a quarrel at the Dedham Assembly, which is capable of involving all Europe in a new war". Assembly rooms were constructed for social gatherings and balls and funded by private subscription. They were popular throughout the 18th century and early 19th century and assembly rooms were built all over provincial England. By the 1830's, the Dedham balls, held three or four times a year, had become famous throughout the county. The splendid affairs ended in 1870 although Hunt and County balls were restored in late Victorian times.

The Dedham Assembly Rooms were later to act as a club for local gentry before temporarily falling into disuse. At the time William Hewitt commenced his renovation, the building had been taking over by a local antique dealer and was being used as a furniture store.

Until recently the present building was thought to have been constructed in 1810 but architectural details hidden within the structure suggested it was much older. As part of the refurbishment work a historic study was carried out by the architectural historian, Paul Drury, and this included dendrochronology dating of the structure. The condition of the existing frame proved ideal for dating and the frame has now been attributed to a construction date of 1744-45, making it one of the earliest surviving purpose-built assembly rooms.

Ninety years ago, through the far-sighted action of William Hewitt, the once magnificent Assembly Rooms were rescued from their diminished status and given a new lease of life. The refurbishment that has just been completed through the generosity of various trusts, councils and individual patrons will enable this historic structure to serve the community in the 21st century.