Chief of the Boat (COB) US submarines

In US submarine service in filums, the rank/rate of Chief of the Boat (COB) is often mentioned. I believe that this is the most senior non-commissioned rate on board US submarines. Is there a similar rank/rate on board Royal Navy submarine service in the nuclear subs in service nowadays?  

I would presume the senior non-commissioned person on board a Brit Sub is either the Chief Warrant Officer or Chief Petty Officer.
Jimsigs

Would this be it?

"The master-at-arms is a ship's senior rating, normally carrying the rank of chief petty officer or warrant officer, the MAA is in charge of discipline and is addressed as "Master" if holding the rank of chief petty officer, even if the rating in question is a woman, she is still addressed as "Master" and known as the master-at-arms. The MAA is assisted by regulators of the Royal Navy Police, of which he is himself a member. He is nicknamed the "jaunty", a corruption of the French gendarme, or the "joss/jossman". The non-substantive (trade) badge of an MAA is a crown within a wreath."

Thanks for that Weedo. That's cleared that up.