Simmons Gainsford, Part of the Sumer Group, Joins Forces with Riordan O’Sullivan & Co
Simmons Gainsford is delighted to announce that it has joined forces with Riordan O’Sullivan & Co, a respected North-West London practice established in 1968. This acquisition marks another important step in our continued growth journey with Sumer.
Founded by John Riordan and expanded by the former and current Partners and staff, Riordan O’Sullivan & Co has earned a reputation for delivering high-quality, personalised accounting and advisory services to a loyal client base. The team’s deep expertise and client-first approach have established the firm as a trusted name in the business community.
Following the acquisition, Riordan O’Sullivan & Co will be rebranded as Simmons Gainsford and will continue operating from their existing offices in Kensal Rise. This arrangement ensures continuity for clients and staff alike, while still benefiting from the broader support, infrastructure, and service offering of the wider group. The firm’s team of three Partners, James Riordan, Paddy McNamara, and Kumar Perumal plus 16 professionals will join Sumer Group’s growing network of over 2,500 colleagues across more than 50 offices nationwide.
The acquisition reflects Simmons Gainsford’s strategic focus on partnering with like-minded firms that share its values and commitment to client service, while respecting the importance of local presence and relationships.
Darren Hersey, Senior Partner at Simmons Gainsford, commented: “We are delighted to welcome Riordan O’Sullivan & Co to our group. Their excellent reputation and strong client relationships perfectly complement our mission to champion SMEs throughout the UK. This merger represents another significant step in our ambitious growth strategy.”
Kumar Perumal, Partner at Riordan O’Sullivan & Co, added: “Joining Simmons Gainsford marks an exciting new chapter for our firm. Our clients will benefit from enhanced service capabilities while maintaining the hands-on personal relationships we know they expect and value. We’re proud to join an organisation that shares our commitment to supporting SME businesses and the communities they serve.”
Simmons Gainsford were advised by Dickson Minto and Riordan O’Sullivan & Co, by Burlingtons.
About Simmons Gainsford
First established in 1948, Simmons Gainsford is a multidisciplinary firm of chartered accountants and business advisers. The acquisition of Riordan O’Sullivan & Co brings our total number of Partners and staff to over 200, based mainly in Central London, with additional offices in Sussex and Gibraltar, and now North-West London.
With the support of the Sumer Group, Simmons Gainsford embarked on an ambitious growth journey in 2023. This partnership empowers the firm to pursue strategic acquisitions, bringing in businesses that share its entrepreneurial mindset and vibrant culture.
About Sumer
Sumer is the UK and Ireland’s leading mid-market accountancy practice delivering professional support to small and medium-sized enterprises (SMEs) across England, Scotland, and Northern Ireland. It is a top 15 UK accountancy practice on a mission to champion SME businesses and offer local delivery supported by national expertise.
Since its inception, Sumer has grown rapidly through acquisition. It now employs over 2,500 champions, with more than 50 offices, and generates an annual turnover of over £217million, emerging as a key accountancy player.
June 2024 saw the launch of Sumer Law, which provides legal services to Sumer’s SME client base, initially focusing on corporate, commercial and employment advice.
More recently, Sumer also launched Sumer Agriculture, a service line supporting farmers, landowners, and rural agricultural businesses.
Sumer’s strategy revolves around only acquiring leading regional practices that share the same ethos, values and approach. This in turn forms regional Hubs throughout the UK, focused on the SME market.
The Hubs announced so far include Carpenter Box, Cowgills, DPC Accountants, EQ Chartered Accountants, HW Fisher, Jerroms, Monahans, RMT Accountants, RT Marke & Co, Scrutton Bland, Simmons Gainsford, Sumer Northern Ireland, and Sumer Law.
Sumer provides Hubs with access to a broader range of services for clients, technology and compliance support, funding for further acquisitions, and opportunities for Hub colleagues.
To find out more about Sumer, visit our website: sumer.co.uk
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