National Physical Laboratory. The UK's Metrology lab - metrology being the science of measurement. Metrology labs around the world maintain the standard measurements that all other measurements are based on (Meters,Seconds,etc).
The NPL can be seen in the film "The Dam Busters", when Barnes Wallis uses the ship tank to test his model bouncing bombs.
Employed Alan Turing to help construct the Ace computer, one of the first true computers (although Turing and the NPL parted ways with some ill feeling).
The America equivalent is NIST.