In 1937 HMS Effingham was extensively refitted and re-armed as a light cruiser. Her 7.5-inch guns were replaced by nine 6-inch and her single 4-inch AA guns by twin mountings. Her two funnels were replaced by one, unraked, to give her an appearance markedly similar to that of the later Leander class.

On 18 May 1940 HMS Effingham (Capt. John Montagu Howson, RN) was carrying the 2nd Battalion, South Wales Borderers, as well as other troops, from Ankenes to Bodo.
Traveling at 23 knots, outside the Norwegian Leads to minimize the risk of air attack, she was only 1 hour away from her destination when she struck a rock in the Fasken Shoal, near Harstad, between Briksvaer and Terra islands in position 67º17'N, 13º58'E.
Ironically, the rock was clearly marked on the navigational chart, but it had been obscured by the navigator's penciled track, and the ship was dead on course! Luckily, there were no casualties, but the ship, impaled on the rock, flooded and could not be moved. She was declared a total loss. The ships crew was taken off by HMS Cairo, HMS Coventry, HMS Echo and HMS Matabele. She was finally destroyed by torpedo and gunfire from HMS Matabele to prevent her capture by the Germans on 21 May 1940.

Commanding Officer:
Capt. John Montagu Howson, RN
17 April 1939 - 18 May 1940