Previous Answer
Hint: This photo, taken in 1975, shows the north end of a tunnel no longer in use for navigation, at the heart of the Midlands canal network. Can you identify the tunnel?
Answer: The photo shows the northern entrance to the original ‘Brindley’ Harecastle Tunnel (opened 1777). Although often thought of as a single tunnel, there are two separate parallel canal tunnels. The original tunnel had a network of smaller canals that lead to mines at Goldenhill, in which James Brindley, who designed the tunnel, had a share. Operation of the canal access to the mines ceased in 1820, when it became unsafe. The original tunnel was 2,630 metres long, had no towpath, and a low ceiling. It’s limitations became obvious soon after opening, as it became a bottleneck on the otherwise successful Trent & Mersey Canal. In the 1820s, Thomas Telford was commissioned to build a new tunnel of slightly greater dimensions, which opened in 1827, complete with towpath. This is the tunnel in use today, although the towpath was taken out in the 1970s, having been disused for many years owing to collapse. The original Brindley tunnel remained in use until the late 19th century, and has not been inspected throughout since the 1960s; it is now fenced off (since the photo was taken) to prevent access. Thanks to John Fletcher for the photo.
Correctly guessed by: Mary Bithell, Jerry Bolter, Ivan Cane, Tony Clayton, Ian Cleathero, Chris Davey, Rodney Hardwick, Andy Lintern, Kenneth Nelson, Gwenyth Salt, Dave Turner, Cyril Wood and Jack Wootton.