The Sexton is marked with the badge of the 86th Hertfordshire Yeomanry Field Regiment Royal Artillery, a volunteer reserve who converted from towed gun to SPG's in 1943 and landed on nearby Gold Beach. In fact, this unit began firing from their landing crafts before they'd even hit the sand, sending a constant volley of 25lb shells onto the defences.
Due to the expected high levels of ammunition needed to breach the beach defences, some Sexton's (and Shermans) carried extra ammunition with them - towed behind the vehicle in sealed 'sledge' known as a Porpoise. These metal containers are extremely rare and so this location is worth a journey just to check it out.