By Geoff Adams-Spink
Age & disability correspondent, BBC News website
A designer who has spent most of his career working on parts for Formula One cars has come up with a new, off-road wheelchair.
Mike Spindle decided to redesign the wheelchair from scratch
The Trekinetic K2 dispenses with the old tubular chassis and uses a carbon fibre monocoque instead.
Designer Mike Spindle was inspired to create the off-road chair when he saw someone wheeling through an airport lounge.
The K2 was launched at the Mobility Roadshow in Gloucestershire.
Mr Spindle has spent the past five years designing the wheelchair from scratch.
After the designer spotted a man in an airport departure lounge, in a metallic purple wheelchair, it occurred to him that somebody ought to be able to do an awful lot better.
"Much to my wife's disappointment, I started sketching this out on the back of an airline boarding pass," he told the BBC News website.
Five years later - a development phase that Mr Spindle describes as "extremely difficult" - Trekinetic chose the Mobility Roadshow to unveil a radical new design.
The K2 has three wheels - two large ones at the front that can take mountain bike tyres - and a smaller one at the back.
The company says it is ideally suited for off-road use but can be just as useful in towns and cities too.
The wheels have an easily adjustable camber so that the chair can have a slimmer profile for going through doorways and a wider - and more stable - 24 degree camber for outdoor activities.
The umbrella is the most conventional thing about the K2
The wheel tilt can be easily altered by rotating a cross shaft underneath the seat: at its slimmest, the K2 is 710mm wide and when fully adjusted it broadens out to 870mm.
Trekinetic had originally set out to design a new, modern and different design: the chair's off-road potential came after prototypes were shown to a group of wheelchair users who said they were unable to tackle more difficult surfaces in their current chairs.
The company thinks the K2 will appeal to relatively active people with good upper body strength, although push bars are available as an option.
Marketing information for the K2 stresses designer chic and desirability with black being the predominant colour.
The K2 owes a good deal to automotive innovation in its own design.
Mr Spindle compares the tubular chassis used by most wheelchairs to the one found on vintage cars.
"In fields of engineering such as F1, they have dispensed with the chassis idea and gone to what they call a monocoque," he explained.
"With a car you now have a very strong basic shell and you bolt all the components to that. With this, we've made the seat a sculptured shape to suit the user's body and we've made it out of carbon fibre which is extremely strong."
The K2 is consequently extremely light - with the quick-release wheels removed it weighs about 9kg.
Weather-proofing is by means of a golfing umbrella which attaches to the base of the seat.
And Trekinetic says that the K2 can be folded up in about eight seconds.
Mr Spindle says the three-wheeler design lends itself much better to off-road use: with four wheels on an uneven surface, one wheel ends up losing contact.
Trekinetic says three wheels are better than four
"Then, you're pretty much beached until someone comes along."
Trekinetic plans to produce about 10 chairs a week from its plant at Uxbridge, Middlesex.
In spite of the fact that its website was launched a month ago without any publicity, the company says it has already had 1,600 hits and has received enquiries from as far away as South Africa and the USA.
The Mobility Roadshow is at Kemble Airfield in Gloucestershire from 8-10 June.