The deal is Solomon's first step towards creating a national advice business serving in excess of 50,000 clients.
Solomon will take full ownership of Beaufort Financial and its discretionary fund management arm, You Asset Management - though Beaufort chief executive Derrick Dunne and co-chairman Simon Goldthorpe will both join Solomon's executive team.
Thompson founded Solomon last year with Darren Sharkey, who until late 2020 was managing director of Quilter's national advice business.
He launched the business to create a "technology-enabled national advice business" dedicated to holistic and hybrid advice and high-quality customer service to mass affluent customers.
Solomon is backed by American private equity house JC Flowers which is perhaps most notable in the UK for backing Interactive Investor before its sale to Abrdn.
Thompson, who left Quilter in mid-2020, said: “Over the years, Simon, Derrick, [co-chairman] Andrew Bennett and the team have built tremendously successful businesses in Beaufort Financial and You, earning great reputations in the process.
"The complimentary businesses provide a significant and strong set of foundations on which we can build, with a shared vision for the future. The talented professionals they employ and the proposition they have developed is second to none."
Beaufort Financial, which is Beaufort's network arm, and You will retain their own brand identities and control over day-to-day operations.
Goldthorpe said: “The deal with Solomon is a positive, natural and planned next step for the business and one about which we are extremely excited.
"We partnered with Solomon because the quality and vision of its leadership team, combined with the strength and track record of its financial backer, will provide us with the platform to set new standards in how financial advice is delivered in the UK.”
Last year private equity back advice business Socium Group withdrew its offer to buy Beaufort after the two companies were unable to agree terms.
Beaufort was established in 2012. Its DFM arm has assets under management of £1.4bn.