The announcement follows Alfa Romeo's 10% year-on-year sales slump and a poor showing in the latest JD Power survey – it came last out of 33 manufacturers in a study which included customer satisfaction ratings, build quality and dealer service.
Owen had joined the Italian carmaker's UK operation in May, 2002 from his previous post as managing director of Fiat Auto in Denmark.
One Alfa Romeo UK insider said: “We can't make a secret of our performance. It's been lamentable and change was inevitable.
“But Glyn parted on very good terms with the company and he's now taking a well earned holiday. He'll be missed.”
Lester, 47, wss group sales director of AutoLogic Holdings plc, Europe's largest independent finished vehicle logistics supplier, which provides a full range of logistics services to the automotive industry.
With almost 25 years' experience in the global automotive industry, Lester spent the first nine years of his career in the service and parts side of the business, and more than 15 years in car sales and marketing at Ford Motor Company and Jaguar.
He has held a wide variety of sales and marketing positions, in both Europe and North America, and was director of Jaguar's UK operations from 1996 to 2002.
Alfa Romeo has already invested £2m upgrading its dealerships. Last month it announced it wanted to separate itself from Fiat in showrooms and develop a unique identity in sales and aftersales.