Next to Anglian, Everest are probably the best known double glazing company in the UK, and like the Norwich-based firm, their history has had its fair share of twists and turns.

Everest, headquartered in Cuffley, Hertfordshire, began life in 1965 and now employees over 900 sales consultants and 700 installers across the UK. The company has two manufacturing sites – Treherbert in Wales and Sittingbourne in Kent – as well as a number of installation and customer service centres.

As one of the first names in the double glazing industry, Everest performed well in its early years, but it took until the 80s for it to really cement its place in the public consciousness. A famous TV advertising campaign saw Ted Moult, the farmer and TV personality, drop a feather in front of a window at the Tan Hill Inn – Britain's highest, and possibly draughtiest, pub – and watching as it fell vertically onto the sill.

The ad, together with its slogan of 'Fit the best. Fit Everest" is still widely remembered, so much so that it was remade in 2009, with Irish TV presenter Craig Doyle in the Moult role.

Up until the 90s, Everest was owned by building materials group Caradon, now part of Novar plc, but slowing trade and a period of stagnation lead to a 1999 sale to Brian Kennedy for £47 million. Kennedy, owner of the Sale Sharks rugby team, prompted a period of diversification at the firm into kitchens, solar panels, flat roofs, garage doors, driveways and security systems, mirroring Anglian's rebranding into a full-range home improvement company.

In 2003, Kennedy sold part of his stake to management for £63 million, later adding to his shareholding to take it to 66%. Four years later, the Cheshire-based entrepreneur sold another chunk of his estimated £100 million stake in a deal which valued the business at £150 million, re-investing the vast majority back into the company. This allowed private equity firm Hutton Collins to take a 25.1% share, with the remainder currently held by Kennedy and Everest's management.

In June 2010, Everest received a bought of negative publicity after an investigation by consumer group Which found the firm, alongside Anglian, Weatherseal and Safestyle, of making false claims about its products or using hard-sell tactics – charges which the company vigorously denied.

Since then, the company's performance has matched the other big names in the double glazing sector. Sales may be down, but it seem to be weathering the storm fairly well, with talk as recently as October 2009 about potentially taking the company public in the near future. Whether this happens remains to be seen, but it's a good an indicator as any of the way the company sees itself going forward.