The NPL, as it's known locally, is respected as a centre of excellence in the specialised field of measurement and time, based at its HQ in Park Road, Teddington.

But this weekend, the annual one-day opening of the NPL's Bushy Park House threw a spotlight on the wide-ranging and mostly unknown activities of its 500 scientists, engineers and researchers.

For instance, in 1979, NPL was called upon to weigh the supersonic airliner, Concorde, to ensure it conformed to the Civil Aviation Authority's rules.

Giant scales calibrated by the NPL were positioned beneath each of the aircraft's wheels to gauge the weight, which without fuel or passengers was recorded as 78.700kg, or 78.7 tonnes. 

Over 2,000 visitors celebrated World Metrology Day at NPL's Bushy House Open Day (Credit: NPL)

Another unexpected partnership was between the NPL and the crisp makers made famous by Gary Lineker - Walkers Crisps, based in Leicester and the UK's largest snack manufacturer.

At the time Walkers made 80,000 slices of potato per minute and they had to be within a tolerance of 0.05mm thick for the crisp to cook perfectly.

According to NPL: "The dimensions are vitally important as is the equipment to produce them. Any thinner or thicker and the slices would have to be thrown away.

"NPL helped assess Walkers processes and confirm that they were operating within tolerance to minimise waste and ensure the perfect crisp was produced each time.

"So do not take your humble pack if ready salted for granted in the future."

The Teddington scientists also have the distinction of inventing Super Black -officially the blackest black in the world and a coating which absorbs all light - which is used aboard satellites as well as other sensitive optical instrumentation.

The opening of Bushy House also gave visitors the opportunity to learn about scientist Sir Alan Turing, who invented electric computing and worked at the NPL after the Second World War, but is most famous for cracking the Enigma code machine at Bletchley Park. An exhibit showed the £50 which shows his image and the letter confirming the honour from the Governor of Bank of England Andrew Bailey to the NPL.

(left) Giant scales under the wheels to weigh Concorde and (right) and photos of code breaker Alan Turing alongside his £50 note

Also on show in the beautiful but seldom accessible grounds of the 17th century house was a drone which hovers 110 metres above earth in the Oxford area to check the imagery produced by satellites, revolving around Earth. 

Cauliflowers are a surprise item in the A-Z index of NPL work but scientists have developed imaging technology which can be integrated into a fully automated harvesting robot which can tell when the crops are ready.

Another unusual task undertaken was testing the effectiveness of pet food on the glossiness of cat fur. A leading pet manufacturer commissioned NPL to build a 'fur glossiness testing rig' so they could evaluate and measure how cat fur glossiness changed with different diets.

NPL has also been involved with the National Lottery to make sure all the balls are exactly the same weight and size. Any difference could mean one number coming up more than others. 

A host of activities including the liquid nitrogen show attracted a crowd (Credit: NPL)

The engineers created GO and NO GO metal rings which the balls were passed through with a difference of 0.0254 of a millimetre to make sure they passed through the larger one but stopped by the smaller one.

When the travel company Expedia wanted to know where in the world has the bluest sky, they called in the NPL which developed a specially designed instrument to 'measure sky colour' - Brazil was the winner. 

To learn more about the work of the National Physical Laboratory, visit its website here.