A son of Brutus and brother of Albanactus and Kamber.
After the death of their father, the three brothers divided Britain among themselves. The region ruled by Locrinus was named Logres in his honor. Albanactus had been killed by invading Huns, Locrinus and Kamber joined forces and drove the Huns out of Britain.
Among the captives taken was a beautiful maiden, Estrildis, whom Locrinus wanted to marry, but he was already betrothed to Gwendolen, the daughter of Corineus of Cornwall. Forced to honor his commitment to Gwendolen, Locrinus took Estrildis as his mistress and hid her in London. For seven years he visited her in secret, during which time Elstridis bore him a daughter, Habren, while Gwendolen bore him a son, Maddan.
After the death of Corineus, Locrinus deserted Gwendolen and made Estrildis his queen. Gwendolen went back to Cornwall and mustered an army, which she led into battle against Locrinus near the River Stour. Locrinus was killed, and Gwendolen had Estrildis and Habren drowned in a river that she decreed would thenceforth carry the name of Locrinus’ daughter. The river became the Sabrina to the Romans, and is today known as the River Severn. Gwendolen became the queen of Britain.
In Sommer’s work a Logres (or Logryn) can be found, which is said to have been the successor of “Brutus en Bretaigne”, perhaps this could be Locrinus.
Historia Regum Britanniae | Geoffrey of Monmouth, c. 1138