[2] The model was introduced in 1981, continues in production, and sells well, despite the fact that Numatic never advertises Henry and retains no PR agency.

[1] During a Lisbon trade show visit in the mid-1970s, Duncan and one of his sales-staff decided to dress up their latest Numatic model with a piece of ribbon and Union flag badge to resemble a hat.

The next day Duncan noticed an amused reaction from passers-by at the customised vacuum, which prompted him to ask his advertising specialist back home to design a more professional looking face for Henry.

[4] In 1981 Henry became the first Numatic International model to have a name on its lid, which had become to look like a Bowler hat, replacing the 'Numatic' brand logo.

In 2014, still the company's sole owner, Duncan was listed at #96 on Management Today's Britain's Top 100 Entrepreneurs, and was said to have a worth of £103 million,[7] estimated to have increased to about £150m in 2021.

Depending on the size of the head or body, the distance between the eyes and mouth can vary (excluding earlier models, as the faces were originally three stickers applied to the vacuums by hand).