Longrose Buccleuch currently operates The Mercure Dolphin Hotel, Southampton, the DoubleTree by Hilton Sheffield Park Hotel, and the Best Western Mosborough Hall Hotel, also in Sheffield.
There are another seven hotel management deals in the pipeline, with two expected to be completed by the end of 2012, and the rest coming to fruition in the first quarter of 2013.
Legacy chief executive Andy Townsend said he wanted to extend the firm into the branded hotel sector.
"We are seeing consolidation in the events agency market, and as that happens, agencies will become more efficient in who they do business with," explained Townsend.
"That will clearly favour the branded hotels."
Townsend and Legacy managing director Jim Gordon join Longrose Buccleuch directors Garin Davies and Andrew Rouse on the board of BHM.
Davies said: "The meetings and events market has changed a lot over the past few years and people want to impress that they aren’t doing things frivolously.
"That is why the branded hotels are doing well – events planners know they are going to get consistency above everything else. That reassurance is very important for the customer."