 On the latter line, only tilting trains can reach this maximum speed due to the difficult track geometry.The 67-mile long HS1 line connects London to the Channel Tunnel, with international Eurostar services running from London St Pancras station to cities in France, Belgium, and the Netherlands at 186 mph (300 km/h).That line is also used by high-speed commuter services from Kent to the capital, operating at top speeds of 140 mph (225 km/h).