A window and door company is expanding sales by 30% a year thanks to its patented design – and a phone call from Manchester United.

Frameless Glass Curtains made turnover of £1.5 million last year and is exporting to Sweden, Spain, Germany, the US and Australia.

It makes slide-and-fold single, double and triple-glazed doors and windows without frames – known as mullions – from its factory in Lordswood, Chatham.

Its products are capable of withstanding 120mph winds, and the company has attracted blue-chip clients such as Audi and Aston Martin.

The company also installed floor-to-ceiling doors and dividers at Manchester United’s Carrington training ground, with a glass partition separating the first team squad from other people in the canteen.

“That legitimised the company,” said managing director Gary Beresford.

“Once you get Manchester United people think you must be good.

“They just phoned up and asked for a quote. It was a really big job at the time.”

After a 30-year career in advertising, Gary launched the business eight years ago after he and his son, Paul, bought the licence to make the product from “a guy in Spain”.

They redesigned the concept to create the bifolding doors sold today, adding the double glazing element and engineering the product to comfortably offer a 10-year guarantee.

“The product wasn’t very good so my son and I designed our own,” he said.

“People might have thought of this idea before but the technology wasn’t there. We came along at the right time.

“We had faith in it but, being honest, it was very slow to start with because we had to convince people that it was a good product. Now you just have to look at the reviews on our website.”

Since then, the firm has become a victim of its own success. Originally operating from a barn in West Malling, it moved to Lordswood four and a half years ago.

It employs 20 people, including three teams installing at homes and businesses every day, but has reached capacity at its present home.

“We can’t stay here,” said Gary, who lives in Larkfield. “We have run out of space. Sometimes you can’t move downstairs.

“We can’t go out and do TV advertising because we wouldn’t be able to cope with the extra work.”

The firm is currently in negotiations with the council to build a factory in Medway, which it will own outright, and hopes to gain planning permission next year.

It aims to invest £1.2 million in its new premises, with the goal of making and storing off-the-shelf products and expanding the workforce to 50 people within 18 months of opening.

With the new factory will come reduced delivery time and cost. At present, an order takes six to eight weeks and is priced at about £7,000.

Gary said: “You get what you pay for. You can’t get this anywhere else. We are the only ones in the world who do it.

“The product sells itself. It’s very simple and the view is unbroken.

“I’ve got them at my house and it’s bright and cheerful. We say we bring the outside in.”