But the management said they also had a customer list of ordinary people around the world who are sticklers for formal dress.
"Period dramas like Downton are clearly helping to drive a resurgence," said owner Matthew Barker.
"We are in demand for balls, dinner parties and for the judiciary. And there is a huge market of people who love to dress up.
"The real boon has been the internet, which has made us a global business. We have customers in America and the Far East."
When Barker joined the company 25 years ago, it was producing 10 collars a week. Now it produces 1500.
One manufacturer in Sydney posts a consignment of its collars every month to be starched and returned.
The laundry deals in winged collars, turned-down collars and round-edged Eton collars.
Starched collars were standard attire in the Downton era, when men would wear the same shirt for up to a week but change the collar daily.
Men lower down the socio-economic scale would wear collarless shirts during the week but add a starched collar on Sunday.
There were 6000 domestic laundries in Britain before World War I but they began to disappear in the 30s when making shirts with collars proved more practical.
Barker said the laundry owed its reputation to a lady called Alice Allen, who worked for 67 years in the Esher and Royal Windsor Laundry in Kingston, from the age of 13 until it closed when she was 80.
Aged 83, she was hired for her expertise by Barker.
"She honed our skills and gave us the edge we have today," he said.
"I would bring her down once a year, put her up in a hotel by the sea for a week, and she would come in to give us advice."
Barker lost Allen's contact details when the laundry was damaged by fire in 2005. He does not know if she is still alive.
"She was a great old lady. I would love to know if she's still out there," he said.
"We lost most of our factory in the fire. The only part that was saved was the collar department, because a roof fell on top of the machinery and saved it. You could say I was lucky, because most of it was irreplaceable."