Former Tour de France winner Sir Bradley Wiggins is among the race favourites along with Nairo Quintana, second behind Britain's Chris Froome in this year's Tour.
This year's race starts on the Scottish Borders and will move through the Lake District, Snowdonia and Dartmoor before concluding with a showpiece finish in central London.
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David Cameron will use a speech today to set out plans for patients to be able to access hospital services seven days a week.
The young Labour supporter seen celebrating an impromptu photo with Ed Miliband has defended her desire for an early campaign selfie.
An unsettled weekend of weather forecast as conditions turn wet and windy from the west tonight and slowly clear eastwards through tomorrow