Locals expressed their concerns after HS2 tunnelling caused a mystery brown foam to spew out of the ground from underneath a west London rugby club. Work on the controversial project was stopped for several hours on Saturday after dog walkers watched on in horror as the bizarre substance bubbled up at Ruislip RFC on Saturday. HS2 workers moved to seal off the area after the hole opened up which was “most likely caused” by one of the tunnelling machines passing through a small pre-existing borehole. Despite the slurry pool being cleared away, locals raised concerns as to what could happen when digging passes under populated areas as the £100bn project continues to bore 13 miles of tunnels towards Euston.