That tunnel looks to be this one I think https://maps.google.co.uk/maps?q=llangothlen&hl=en&ll=52.954016,-3.063812&spn=0.006464,0.025921&usq=llangothlen&t=h&z=14&layer=c&cbll=52.954002,-3.063755&panoid=Bqy5l1K91zMGjFQHeUE8Rw&cbp=12,163.84,,0,15.01
even google have ridden the Llangollen canal :)