In some ways Plunkett's approach was closer to that of an artist-craftsman, particularly his direct involvement with making and his minute attention to detail. In the case of the Reigate Rocking Chair (1964), which won a Council of Industrial Design award in 1968, Plunkett made the frames of the first 24 models himself. He also made one-off pieces, such as decorative screens, for churches and civic buildings.
The sculptural quality of his designs was central to their ethos. Even at the height of his success, Plunkett's furniture was only ever batch-produced in limited quantities, which explains why his work is less well known than his more high-profile contemporaries, such as Robin Day. Plunkett preferred to keep the operation small so he could retain creative control. "I don't want my furniture to lose its character," he told the Guardian in 1964.
One of his most successful and long-lived designs was the Kingston Range (1967), a flexible seating system, later known as the Plunkett Plan, in which chairs, sofas and benches were created from rows of individually upholstered foam rolls glued to plywood boards, mounted on an aluminium frame. The Epsom Range (1966) worked on similar principles, but used pre-formed plywood strips to create curved seats. The Epsom Swivel Chair, resembling segments from an orange, was particularly arresting.
After selling his company to Giroflex in 1977, the designer set up a new firm called Plunkett Plan Ltd the following year. Having retained the rights to his earlier designs, he carried on producing furniture to order until as recently as 2005, latterly mainly for Russell & Bromley, his most loyal and longstanding client, where his furniture is still in use in some stores.