Naval commanders in London and Paris have confirmed that two of their nuclear-armed submarines collided earlier this month in the Atlantic Ocean. HMS Vanguard and its French counterpart Le Triomphant were on separate missions when they hit at low speed. Vanguard returned home with dents and scrapes on its hull, but the head of the Royal Navy insisted the boat’s weapons capabilities had not been damaged.Le Triomphant is said to have fared worse. She limped back to Brest with extensive damage to her sonar dome. Submarine warfare experts say modern anti-sonar technology is so effective neither boat may have known the other was there. Le Triomphant is part of France’s four-strong nuclear submarine fleet. HMS Vanguard is likewise one of four British subs carrying Trident nuclear missiles.