In first-class cricket, Walker had three seasons where he finished with a batting average of over fifty: in 1996, 2004 and 2006. 1996 saw Walker hit the highest score of his career to date, on his way to 606 runs at an average of 60.60. Against a Somerset attack without Andrew Caddick, Walker compiled 275 not out in nine-and-a-half hours before his captain Trevor Ward declared the innings at 616/7. The Daily Telegraph's Christopher Martin-Jenkins wrote of the innings: "It was an innings of style and substance, memorable for powerful driving through the off-side and hearty pulling whenever a persevering but ordinary Somerset attack became impatient with line and length and tried to extract a spring in the pitch which simply was not there." It remains the highest score by a Kent batsman at the St Lawrence Ground.