Visitors to London's Euston Station may get a brief encounter with a difference if they wander into Threshers, M&S Simply Food or Whistlestop on Friday (May 12). Staff in these outlets, all operated by SSP UK Rail, will be wandering about in their underwear. Although whether they will choose to be scantily clad or simply adopt the superhero approach of wearing briefs on the outside of their trousers remains to be seen. But fear not, it's all in a good cause. The day has been designated 'Y-fronts for Why Day' in aid of charity Railway Children to prompt people to ask why there are 120 million children sleeping rough in the world.