 The original Main Stand burnt down in 1921 , and was replaced by the current stand before the 1922 – 23 campaign . The ground underwent extensive redevelopment during the 1930s , and the capacity by the start of the Second World War was 30 @,@ 000 . Floodlights were installed before the 1953 – 54 season , but it was 20 years before any further modernisation was carried out . In 1973 the Bobbers Stand became all @-@ seated , and in 1985 the grass pitch was replaced with an artificial playing surface ; it quickly became unpopular and was derided as " the plastic pitch " . 
