It's just 50 miles from the Thames at Chertsey to the Channel at Shoreham, and this route does it in style.
Its main draw is the 37-mile Downs Link, an unpaved rail trail across West Sussex. Britain has few continuous railway paths of this length. It's gravelly, sometimes muddy in wet weather, and therefore best suited to hybrids, gravel bikes, sturdy tourers and even MTBs.
North of Guildford, route 223 uses minor roads and functional if uninspiring roadside paths.