Testing of the world’s fastest, most powerful supercar has hit the UK, as development continues to ready the 249mph Bugatti Veyron for its September launch.

Caught in the (very) long lens of AM’s spy photographer, customers and the curious are unlikely to get a gawp at the 987bhp W16-powered coupe in any showrooms, even a one-off like McLaren’s retailer in Park Lane.

“There aren’t any plans for official showrooms at the moment, partly due to the cost of supplying a demonstrator,” says a spokesman. Bugatti is handling orders for the 1m euro supercar from its factory in Molsheim, France. For servicing, customers are likely to be directed to the Bentley dealer network.

To date, Bugatti has around 50 “serious expressions of interest”; production will be capped at 500 units. That’s quite a gap between demand and supply: millionaires are no doubt waiting to see how the car ends up before paying the 300,000 euro deposit.

The concept was first shown almost six years ago, and initial deliveries were due for 2003. That summer, press drives were cancelled after VW chairman Bernd Pischetsrieder (a former McLaren F1 owner) demanded a faster steering rack at the 11th hour. A further mishap blighted a demo at the Laguna Seca circuit. Potential buyers had assembled to see the Veyron in action, but the prototype span.

Engineering a car to hit the prescribed targets of 400kmh (249mph) and 1,001PS (987bhp) has proved fiendishly difficult. The Veyron has been plagued by rumours of cooling, aerodynamic and tyre difficulties.

It’s not clear what Bugatti was testing at the British proving ground. According to our spies, drivers were putting the Veyron through low-speed handling tests. No high speed work was visible.

British supplier Ricardo may have been involved – the firm has engineered an impressive gearbox capable of handling almost 1,000lb-ft of torque.