Dan Snow, surveying the landscape around Ypres, hears the recollections of veterans of the Third Battle of Ypres, and maps their painfully slow progress eastwards. As the front line crept towards the ruins of the village of Passchendaele, the men renamed the few landmarks around them to reflect their experience of the place - from Hellfire Corner to Vicious Crossroads. As they advanced, in a series of local battles, the men were afforded little or no shelter, apart from abandoned German concrete pillboxes.