I dont think you could ever accuse DCT and BW as being in a conspiracy together. As I seem to recall DCT have been nothing but a pain in the a**e to BW (and its predessors) since the early 60's. The tunnel is under the guardianship of BW, Dudley MBC and DCT - all concerns ploughing considerable sums of £££ and in DCT's case many (10,000's +) voluntary man / woman hours. Its possible to have this forum thread because the tunnel still survives and is navigable, albeit to the more traditionally shaped vessels (think square peg, round hole). Why would DCT want to stop Joe Public, canal enthusiasts and caving / geology groups going in when they've spent the past 40+ years trying to keep the thing open? It doen't add up sorry. There, I feel much better now!!
Can I offer some ideas / thoughts up on other items pulled up in this thread?
A gate at the Parkhead end was used so that boats locking down / up the Parkhead flight didn't draw the water from the tunnel and slow down the legged boats that were making passage to the Tipton.
The gate at Tipton end I would have thought is principally for security / safety, and to ensure that craft do not try to make their own passage through the tunnel without prior knowledge of DCT. You have to remember that there is not only the tunnel but also additional branch canals in to limestone mine systems (a whole new health and safety issue I would have thought).
The towing service is free - any gratuities are not expected and purely at the discression of the towed vessel. - I checked.
The gauge at the Tipton end replaced the fixed gauge in the portal to allow boats to gauge more easily. It is a fair gauge. The gauge at Parkhead is fixed, and again is a fair gauge. The tug skipper has the final say. They know the tunnel, they know the tug, they know the water movement. The water level has been known to rise up and over the towpath (approx 12") in a matter of minutes.
Any crews that want to leg all the way through can, but need to inform DCT of this so that adequate time can be allowed. The tug still goes with the vessel but stays about 20m ahead so that if any problems were encountered then a quick line can be made and towing recommenced.
Small unpowered craft are not permitted. This is a BW rule, not DCT.
DCT are there to provide a service. They do it well. They want boats to make the passage through - the more the better.
I sound biased because I am as I worked for DCT in the 90's. Its a wonderful piece of construction, and in DCT's hands it has a more secure future than it ever has since (and while) it was built.
Any more info can be found here
http://www.dudleytunnel.co.uk/