The restaurateur, who managed Rick Stein's restaurants before opening his first restaurant - Sam's Brasserie in Chiswick - four years ago, said the average number of diners at the Chiswick branch on a Monday night was now 100 compared with 50 a month ago.
He said: "We're never going to do 2-for-1s, which is what we are competing with from most high street restaurants. The BYO gives value to the customer and creates a bit of a party atmosphere.
"We're obviously not making any money on drink, but we are taking more money on the food and they might have a cocktail or a glass of Champagne still or are having the full three courses that they might not have had before."
Harrison, whose second restaurant, Harrison's opened in Balham two years ago, said bookings were already coming in for Christmas at both restaurants with new £25 and £30 menus proving popular.
He said: "A lot of companies have had to cut back on their Christmas party budgets, but they still want to take staff somewhere they can have fun so we brought in these new menus that make it affordable for them. I think we'll be busier this Christmas than before, even in a recession."