I've never worked with a Bobby couldn't run after someone because they were so unfit, but many (including myself ) due to the weight of equipment and PPE. A 2XL body armour alone weighs about 7kg, never mind spray, peg, cuffs, first aid kit,, radio, clumpy uniform boots, computer or Blackberry, various pads and paper... all wrapped up in a non breatheable outer layer. Distance, no problem (im a runner myself) but it knocks a quarter to a third off your speed, making it a largely pointless exercise. The weight is so bad that many end their careers prematurely due to hip or back problems brought about by the load.
Rather than address the problem some forces have started issuing rucksacks, which makes things worse as the scrambled egg then start issuing laptops and things to carry around.
Most of those one ends up pursuing are younger, more suitably attired, wearing trainers, and often with the benefit of certain South American powdered stimulants...
The fitness test is laughably easy, I'd hardly broken into a jog by the time it ends. Its no measure of actual fitness, is utterly unepresentative of the physical rigours of police work, and unfairly discriminates against women and those of smaller stature...which tends to be non Caucasians. Its a pointless joke.
So they used to put me through a fitness test to check I was fit enough to run after bad dudes, then issue me with such a weight of uniform and equipment that I had little prospect of catching anyone I ran after anyway - coppers could all be 30 stone bloaters and it'd make little practical difference to the sport of foot pursuits. We know Tom Winsor has never been a copper himself, and no where is this more evident.