I'm busy editing the Lancaster Canal DVDs after filming the Ribble Link and Lancaster Canal this summer.
I'm double checking the facts I've put in the draft commentary and these included a mention that Tewitfield is the most northerly point you can navigate to on the main canal system.
A little Googling shows some sites claim Ripon as the most northerly point while others claim Tewitfield. Time to establish a few facts.
I looked at the Ordnance Survey (OS) Grid Reference which shows
SD 51912 73622 for Tewitfield
SE 31565 70848 for Ripon
It is the last set of digits which define the "Northings" which increase as you move north, and, as these are both in the same row of tiles (SE being immediately to the right of SD) it's safe to compare these directly.
This shows Tewitfield as the most northerly point by 73622-70848=2774.
Putting the decimal point in the right place shows this as 2.77 km, that's 1.72 miles.
Now the OS grid system overlays a rectangular grid on the curved sphere of the earth and that inevitably creates distortions, so perhaps that's caused an error.
Looking at the Latitude and Longitude will allow for the curvature of the earth and this shows
54.15613°N, 2.73785°W for Tewitfield
54.13250°N, 1.51843°W for Ripon
This time it's the first part of the reference we want to check, with the Latitude number increasing as we head north. This shows Tewitfield as 51.15613-54.13250=0.02363 degrees further north than Ripon.
Converting that angle into a distance at the earth's surface gives 2.63 km, that's 1.63 miles.
I'm pleased to see the two methods give similar answers. Tewitfield is definitely north of Ripon and the difference is large enough that any small inaccuracies in deciding where the end of the canal is don't matter.
Before the Ribble Link was opened, Ripon was the most northerly point on the connected canal system and I suspect those quoting Ripon are using old information. Tewitfield has been the most northerly point on the connected canal system since the Ribble Link opened in 2002.
The Ribble Link Crossing, along the tidal rivers Douglas and Ribble to reach the Lancaster Canal, is no more, and no less, difficult than the journey along the tidal River Ouse to reach the Ripon Canal so I believe them to be equally connected to the main canal system.
Ripon still has a claim to fame, with the northernmost lock on the connected system being Rhodesfield Lock, about 1 km or 0.6 miles from Ripon.