YOU report that the first tunnel boring machine (TBM) had arrived in Britain from Germany, albeit in more than 1,000 parts to be assembled over the coming months, to bore a 10-mile long tunnels as part of the HS2 route ("HS2 tunnel machines arrive for assembly at UK site", The Herald December 8). My fag-packet Pythagoras calculations tell me that such a machine could bore a tunnel under the mountains somewhere between Arrochar/Ardgartan to rejoin the A83 north of the Rest and be Thankful, of proportions sufficient to allow for the subsequent construction of a two-lane roadway in full compliance with UK road requirements.