Seven fleet submarines are presently in commission, three Trafalgar class and four Astute class. Three more Astute-class fleet submarines will eventually replace the remaining Trafalgar-class boats. One of the three Trafalgar-class boats, HMS Trenchant, was inactive as of 2021 and being prepared for formal decommissioning. The second-last boat of the class, Talent, was reported to have reached the same inactive status in April 2022.
The Trafalgar class displace approximately 5,300 tonnes when submerged and are armed with Tomahawk land-attack missiles and Spearfish torpedoes. The Astute class at 7,400 tonnes are much larger and carry a larger number of Tomahawk missiles and Spearfish torpedoes. HMS Audacious was the latest Astute-class boat to be commissioned.