Posted on April 27, 2015 by editor. Britainâs fleet of nuclear submarines is called Trident. There are four submarines (called Vanguard-class submarines), each with the capability of carrying 16 nuclear missiles. Itâs the missiles themselves that are actually called Trident (Trident II D-5 ballistic nuclear missiles).osted on April 27, 2015 by editor. Britainâs fleet of nuclear submarines is called Trident. There are four submarines (called Vanguard-class submarines), each with the capability of carrying 16 nuclear missiles. Itâs the missiles themselves that are actually called Trident (Trident II D-5 ballistic nuclear missiles).