This building at 1 Market Square was designed by architect Thomas Brine and built by public subscription in 1830 on the site of the old 'Baby Tower', originally serving as public shambles or butchers' market with a covered ground floor of open arches sheltering market traders and a cool butter market beneath; the upper rooms briefly served as a Customs House and later as Assembly Rooms hosting the mid-20th-century Athol Club, complete with snooker tables and a reading room. Around 1889 the building became home to the Manx Bank, passing to Martin's Bank by the 1930s, and it has since housed Barclays Bank for over four decades, retaining its Georgian arcaded ground floor as a distinctive feature of Castletown's Market Square.