The initial castle was probably a large motte and bailey, copying the plan of the castle that D'Oyly had already built 12 miles (19 km) away at Wallingford.[1] The motte was originally about 60 feet (18 m) high and 40 feet (12 m) wide, constructed like the bailey from layers of gravel and strengthened with clay facing.[12] There has been debate over the sequencing of the motte and the bailey: it has been suggested that the bailey may have built first (thus utilising the pre-existing St. George's Tower as the first keep) which would make the initial castle design a ringwork rather than a motte and bailey.[13]