The new outlet will be the firm’s fourth BMW Mini site, following the acquisition of its first three centres in Watford, Stirling Corner and Ruislip earlier this year.
As well as strengthening its presence in North London, it will boost the dealer group’s annual turnover to more than £350m.
The new dealership comprises of a showroom in East Finchley and an aftersales centre in Kentish Town in London.
Including the latest addition, Spire now employs approximately 620 staff members and is one of the 25 largest dealer groups in the UK.
The deal will also allow Hexagon to focus solely on its growing Classic Cars business, based in South Kensington, while providing a secure future for its staff on the BMW and Mini side of the business.
Darren Guiver, Spire’s managing director, said: ‘That has been a cornerstone of our business philosophy from day one. I am delighted to welcome everyone from Hexagon to the wider Spire group and to further our relationship with our brand partners BMW and Mini UK.
‘It is a very well run and highly respected business in a prime location, and I am sure we can continue its long history of success going forward.’