Apparently, at 12' 2" (3.7m), the Stenson Bubble (as the lock is named - you can see why) is one of the deepest locks on the inland waterway system. Stenson is the last of six wide locks on the Trent and Mersey, being 14' (4.2m) wide and 72 feet (21.9m) long, big enough to accomodate two boats at once. Narrow locks are half the width.
There are two boats in here at the moment, even though only one nosed into the picture.
So... time to sit back and enjoy the whole process of passing up through the locks... (You'll have to imagine the sound effects)
Already about a third filled here.
The paddles on the upper gate open to allow the water to fill the central section of the lock. (You can see the upper paddles, but there is also a pair of sluice gates below normal water level.) The lip over which the water is gushing is called the cill and makes a buffer for the upper gates, creating a watertight seal. There is a cill on the lower gates too, but you can't usually see it because it is around four feet underwater.
Almost level. In the photo below, you can see the rack and pinion rod for raising and lowering the paddles. They are worked with a windless or 'lock key' which looks a bit like a large right angled spanner and is carried on board by the boater. (You can see one being used in the very top photo)
Once level, the gates are pushed open. The top gates are easy to move, weighing a mere 950kg each.
Once fully opened, the boats can leave. (If you look carefully, you can spot both boats here)