Heathrow World Distribution Centre (HWDC) is a sorting office for international mail operated by Royal Mail. It is situated in Langley, near Slough, England and opened in 2003. All mail entering and leaving the United Kingdom is sorted at Heathrow World Distribution Centre under tight aviation security standards, following the closure of all other international mail handling facilities in the UK. Not all mail handled at HWDC arrives by air, as road vehicles that formerly arrived in the UK by ferry at Dover, or container ship at Southampton now extend their trip to HWDC by road, instead of entering the Royal Mail network at (now defunct) offices of exchange situated nearest the ports. Outbound mail will usually leave the country by aircraft from the nearby Heathrow Airport.