Hard to date Brit stuff as they did not have the yearly updates like the American iron.
According to Wikipedia that style (the E494A) Intro'd in 49 so as the pic was taken in 51, it must be a 49, 50 or 51.
My son's '48 had the trafficators in the B-pillars and had flip-out vents on the cowl. I just bought a '49 that has the trafficators below the belt line as shown and fixed cowl vents, so you must have a '49 or later.