Gracie Barra Bristol, (BJJ), Can Sönmez, Bristol, UK - 15/10/2013
Brown Belt Requirements DVD, where he calls it the 'Relson' choke. I'm going to go with a more descriptive name, deep grip choke: to establish that grip, you may find it helps to sit up to get it in really deep. As Dean discusses on his DVD, an especially deep grip can help your choke as well as give you authoritative control.
Often people will let you get a grip on their collar from guard, unlike the same situation from under mount, despite the threat being similar. If possible, it's a good idea to open up the collar with your same side hand to help get your other hand in as deep as possible. Like John Will says, this will also take the slack out of their gi.
Once you have it, this deep 'Relson' grip provides three main advantages. Firstly, you get great control, as you can pull them down towards you. Secondly, it could be the beginning of a choke. Lift their chin with your forearm to make some space, then insert your other grip. Due to the depth of your first grip, the second hand doesn't need to go as far. Turn your thumbs inwards for the choke, pulling in with your elbows (don't flare them out).
Even if you don't land the choke, just having the grip will make them start to worry about that choke rather than thinking about passing. Thirdly, it means you can establish a collar and elbow grip. There are various attacks you can do from there, the most common of which are probably armbars, scissor and push sweeps.
Should that grip slip, then you still have a more orthodox collar choke available, or the numerous options from a collar and elbow/sleeve grip, if you established that hold. Should you switch to the standard collar choke, you can try another Roy Dean trick. Shoot your arms out straight, aiming to get your hands to the back of their collar (ideally, gripping right by the tag), then grip as normal. Remember to turn your thumbs inwards rather than out (or to put it another way, turn them away from your face rather than towards it). Turning them outwards will work too, but inwards should be tighter.
If they try to avoid having their posture broken down and lean back, that can provide the perfect opportunity for a sit-up sweep, also known as the hip bump. This makes for a classic offensive combination with the kimura and guillotine. Rise up, reaching over their shoulder with your opposite hand, putting the other behind you for base (often you might find you come up on your elbow first, then switch to the hand). Secure their tricep and whack them with your hip as if you were doing a big step to slowly spin in place. This should cause them to fall off balance. Once you get your knee onto the mat, twist your upper body so that you're effectively doing a take down.
Teaching Notes: The choke doesn't flow directly into the sit up sweep, as you have to release your grip. I still like the conceptual approach of breaking posture then following them up, but I am not certain starting with a choke is the best way to do it. The more orthodox approach would be going for the sit-up sweep first, then attacking as they push back into you with kimuras, guillotines etc, but personally I find myself in the other scenario more often.
Also, I didn't write this directly after the lesson like I normally try to do, so can't remember much. Note to self: don't leave it until a week later to finish your write-up! ;)