In his new role, Pothecary will retain executive responsibility and accountability, as well as providing “strategic oversight of the business and supporting and challenging the chief executive”.
Beaumont (pictured) joined the lender in 2017 as deputy chief executive and last year witnessed a record performance of the company.
Last month TML reported a 10 per cent boost to its monthly record for decisions in principle.
Founder and outgoing chief executive Pothecary said: “Peter has done a fantastic job since he joined us just over two years ago.
“He has identified new opportunities, differentiated the brand with ‘real life lending’, launched buy to let and overseen exponential growth in lending and the team.
“When we set up The Mortgage Lender in late 2014 the intention was to build a strong sustainable business, we have and continue to do just that.”
Beaumont added: “I’m delighted to be taking on this challenge at a time when the hard work of the last couple of years is paying dividends and The Mortgage Lender is going from strength to strength.
“By adding skills and expertise to the team and investing in relationships with our broker partners we’ve successfully created a niche for our real-life lending ethos by focusing on products that will meet the needs of today’s borrowers.
“We have ambitious lending targets for this year, have started the year strongly and are on track for another record year.”
The Mortgage Lender last year completed its first UK mortgage-backed securitisation of residential assets for £238.5m.