Designed as a replacement for the 60 pounder gun the first 4.5in Mk. I guns arrived in 1938 and shared the same carriage as the 60 pdr. The gun itself had a long range which made it suitable for counter battery fire, but its ordnance suffered from low HE content. The Mk. II was issued in 1941 and was mounted on the same carriage as the 5.5in gun. The Mk. I gun first saw action in France with the BEF and around 32 were left behind. It later served in Greece and North Africa. The Mk. II also saw action in North Africa and later in Italy and Northern Europe. The weapon was withdrawn in 1945 and used for training and replaced by the 5.5in gun.