Gallyot is a legal and estates director at pubco Punch, where has has 14 years' experience in the company.
He will advise Irwin Mitchell on its food and drink push while continuing to run his own consultancy firm, which launched in January this year.
Gallyot said he hoped to take advantage of the opportunities in the retail industry with the firm.
He said: “Food and beverage retailing is under significant pressure but it’s important to remember that the disruption in the sector also brings numerous opportunities and a myriad of legal issues that businesses need support with.
“I’ve been impressed with Irwin Mitchell’s approach to this sector and I firmly believe that together we can take advantage of the huge opportunities that exist.
“This is an exciting opportunity for me and I look forward to working with the team at Irwin Mitchell and with its new and existing clients.”
Victoria Brackett, chief executive of Irwin Mitchell’s business legal services team said the appointment would see the firm’s market proposition magnified.
She said: “We are delighted to welcome Stuart to the team. He has a wealth of senior-level expertise in the food and drink industry and he will be able to offer hugely valuable insight into our business.
“I’m confident that he will enhance our market proposition and ultimately further improve our service for our clients.
“Stuart is Irwin Mitchell’s first non-exec director to be appointed and we look forward to welcoming more into other sector groups as we continue to invest in our business team.”