Accents are often influenced by national and ethnic differences, so Welsh and Scottish accents will be different from English accents. Regional accents are affected by the influences of the 'national' accents on their borders, e.g. the more 'Celtic' north of England will have a different sound to the more 'Saxon' south. The west of Scotland and the north of Ireland have similarities due to their proximity and cultural ties. For centuries, the regions were quite isolated from each other as communications were difficult until the days of modern transport, so regional accents had time to become more pronounced and stronger.