Not anymore. That law was suspended a while ago.
I'll clarify that - it's still on the list of items you have to have in the car but there's no enforcement currently.
I work for a local IT / Telecoms company and it's in our staff handbook that they can test us. Why I have no idea given most people catch the train to work and we do nothing dangerous - a vast majority of staff are desk based and answer the phone for most of the day.