Seymour holds the Kent record for consecutive County Championship matches played for Kent, appearing in 196 consecutive Championship matches for the County between 1902 and 1911. He was described in his Wisden obituary as an "indispensable member" of the Kent side who "could never be left out", despite Kent having an excellent side in the years before the First World War. He appeared in 536 matches for the County, a total which places him third on the list of most appearances for Kent.