From Windsor Castle walk to Windsor & Eton Central, train to Slough Bus Station, line 3 bus to Uxbridge, York Road (UB8), then line 724 bus to Watford Junction Railway Station. 1 h 51 min £10. From Windsor Castle taxi to Watford Junction Station. 29 min £107. From Windsor Castle drive to Watford Junction Station. 29 min £5.