Presenting the Royal Navy's Type 23 Frigate, also called the Duke class. With 13 active ships of this class, it is correctly stated that the Type 23 currently makes up the backbone of the Royal Navy. The Type 23 is a specialized anti-submarine ship.
In fact, it was originally intended to be far more specialized than it is, but hard lessons from the Falklands war lead to a rethink of the design. The Type 23 sports Harpoon anti-ship missiles and a battery of capable Sea Wolf VLS-launched anti-air missiles. It is advised, however, to pair it up with its big brother the Type 45 destroyer (Daring class) if you expect a serious missile or aircraft threat.
The below is a recent screenshot of a Type 23 appearing in-game (pre-release):