Annable's London is Norwich above the treble and Cambridge below the treble, but with a 3rds place half lead. But what does that mean in practical terms?
4ths place bell is the pivot bell in Annable's London, the bell whose blue line is symmetrical. It starts out exactly the same as in Cambridge, doing Cambridge places down. BUT instead of the final dodge of those places, it makes 3rds, and then starts doing Cambridge places up! Another way to think of this is: 3rds, 4ths, dodge with treble, make 3rds and 4ths until the treble comes back, dodge with the treble, 4ths, 3rds. You're taking the Cambridge places sections from Cambridge 4ths and 6ths place bells, and connecting them with 3rds at the half lead (when the treble lies at the back).
In Cambridge, the 3 hunts up and the 6 hunts down while the 5 lies behind, and then the 3 and 5 double dodge with each other. In Norwich, the 3 makes 4ths and goes in! (Like Oxford places, if you've rung Oxford Treble Bob.) This means the 6 can't go anywhere, so the 5 and 6 dodge, and then keep dodging. The double dodge in Cambridge becomes a triple dodge in Norwich, and which bells do what has been rotated. In the second half of the lead, the bell that dodges 5-6 up with the treble will then lie and triple dodge down, while the bell that passes the treble in 4-5 (2nds place bell in Cambridge) will triple dodge up (instead of double dodge and lie). Norwich: starts with a dodge at the back. Cambridge: doesn't start with a dodge!
This is pretty easy: all the Cambridge front work is exactly the same! The only difference is that just mentioned—after you pass the treble in 4-5, you will do three dodges at the back instead of two. The place bell that does the reverse of this is the 6: triple dodge down, then hunt to the front (passing the treble in 4-5) and do the Cambridge front work.
As mentioned above, the 3 starts by making 4ths, which causes it to turn around and go in to the front. It passes the treble in 2-3, which in Cambridge is done by the 6. The 3 then proceeds to act like the 6 in Cambridge—lead full, dodge. The lead full occurs while the 2nds place bell is making 2nds, so the bell you take off lead is the same one you will dodge with. Just like Cambridge! Now, the next thing the 6 would do is hunt up to start Cambridge places. But we know the 4 has taken that over. So instead of dodging 4-3, the 3 continues hunting 4-5, which puts it in place to dodge with the treble at the back. I explained what happens next in the "Above the treble" section. The place bell that's the reverse of the 3 is the 5. It begins with triple dodge up, lie, dodge down with the treble. Then it hunts all the way in to the front, dodge and lead (like Cambridge 4ths place bell), then hunt up passing the treble in 2-3. Then make 4ths! Instead of hunting all the way to the back.
Annable's London has a 6th place or plain hunt lead end rather than the 2nds place lead end of Cambridge. So it's slightly more like Primrose than like Cambridge! Norwich itself is a 6th place method, but there are several pairs of Norwich-above methods in which one has a 2nds place lead end and the other has a 6ths place lead end. In fact, if you ring Annable's London with a 2nds place lead end, that's Netherseale! Two methods for the price of one!
While it is certainly possible to learn individual surprise minor methods entirely separately, it is more efficient (and more fun!) if you can be aware of how the methods relate to each other. This does require somewhat detailed understanding of at least one surprise minor method to start out.
Ideally you will have learned Cambridge not as (just) a single long blue line, but as five chunks, one for each place bell. Essentially all this means is that you associate each leadend-to-leadend chunk of the line with the bell that does that chunk in the first lead. It's easy to describe this for Cambridge because each place bell only really does one big thing, and possibly a little thing too. 3rds place bell does the backwork. That's it! 2nds place bell does the Cambridge frontwork, then goes to the back and double dodges. 5ths place bell does that in reverse—lie, double dodge, then Cambridge frontwork. 6ths place bell does a little thing first—lead and dodge—then Cambridge places in 34. 4ths place bell starts with Cambridge places, then dodge and lead.
Learning a method in place-bell chunks gives you more recovery points for when things go wrong in ringing. It gives ringers a language for telling each other where they should be at lead ends. It's also helpful for ringing touches, and to easily be able to ring 6ths place versions of a 2nds place method and vice versa.
It's very important to know exactly which whole pull of each place bell is the lead end, because that is the portion that could change in the situations just mentioned. For example, Cambridge places up (part of 6ths place bell) goes: dodge 3-4 up, 4ths, 3rds, dodge 3-4 up with the treble, 4ths, 3rds, dodge 3-4 up. It is useful to understand this whole thing as a unit, but also good to know that in minor, the final dodge is the lead end. If a bob (or single) were called, you would ring the handstroke in 4ths place as usual, but instead of dodging back to 3rds you would make 4ths, becoming 4ths place bell. If instead of Cambridge you were ringing Primrose, that last dodge would be replaced with hunting 4-5 to become 5ths place bell.
Conversely, the first dodge of Cambridge places down is not actually part of 4ths place bell, which does the rest of Cambridge places down. That first dodge is the end of 3rds place bell. For this reason and another I'll get to below, I like to think of the places surrounding dodging with the treble as the core of Cambridge places, and the dodges at the beginning and end as flourishes that are sometimes included.
The lead end is when the hunt bell, the treble, leads, returning to its starting position. The half lead is when the treble lies at the back, halfway between two lead ends. Knowing where the half lead is in each place bell is useful for similar reasons as the lead end. It can be another recovery point or way to receive confirmation that you're in the right place. And just like there are methods that only differ over the lead end, like Cambridge and Primrose, there are also methods that only differ over the half lead. Ipswich Surprise Minor is Cambridge but with a 1st place or plain hunt half lead.
The half leads in Cambridge (at least on minor) are actually very clear landmarks! 3rds place bell is most obvious, because it makes 5ths under the treble. This is the reverse of making 2nds over the treble at lead end. In fact, the entire half lead is the reverse of the lead end—the place closest to the treble is made, and the other two pairs of bells dodge. The dodges on the front are the last dodge of the Cambridge front work (2nds place bell) and the first dodge of that same work (5ths place bell). The dodges in 3-4 are the last dodge of Cambridge places down (4ths place bell) and the first dodge of Cambridge places up (6ths place bell). This means that one end of Cambridge places is at the lead end and the other end is at the half lead. The possibility for both half lead and lead end to be different in different methods is what makes me think of those dodges as optional flourishes.
Another important way of segmenting methods is by chunks that are below the treble and chunks that are above the treble. This is a vital part of surprise minor ringing! The 41 standard surprise minor methods are all Cambridge, Norwich, London, or Carlisle above the treble (though the lead ends can be 2nds place or 6ths place for each of these except London which is always 2nds place). The possibilities below the treble are a bit more numerous, but it's still much less to learn than by treating all 41 methods as entirely distinct. Apart from being able to mix and match different methods, it's also useful to have yet more recovery points and ways of orienting yourself to the rest of the band. If you're ringing a touch, where you pass the other working bells will change, but passing the treble will always be the same for each place bell.
Since the treble is treble bob hunting, passing the treble in 1-2, 3-4, and 5-6 involves dodging with the treble. Passing the treble in 2-3 and 4-5 is just that, no dodge. There are also some features around passing the treble that are common to all surprise minor methods, because they are what make a method "surprise" or are just part of how method structure works. Before dodging 5-6 down with the treble, you must lie at the back so that the treble can come to you, and after dodging 5-6 up with the treble you must lie at the back so the treble can hunt down. The same is true in reverse at the front—after dodging 1-2 down with the treble, you must lead so that the treble can hunt up. In the standard 41 surprise minor methods, this is *always* followed by making 2nds, so that 2nds place bell always begins by dodging with the treble, leading full, and making 2nds. Whatever bell passes the treble in 2-3 on the way down will then lead full while 2nds place bell makes 2nds. The 3-4 dodges with the treble are always preceeded and followed by places: 3rds, 3-4 dodge up, 4ths; or 4ths, 3-4 dodge down, 3rds.
As a working bell in a surprise minor method, there are four other working bells you can dodge with. In Cambridge, you will meet only two of these bells at the back and only the other two on the front. Which bells are which will change if you're ringing a touch, but in a plain course they can be determined from the cycle 24653. The two bells immediately to either side of you (remembering to wrap around if you're on the 2 or 3) are the bells you'll meet at the back, sometimes called your course and after bells. The other two you'll meet at the front.
Here are some other surprise minor methods to consider trying if you haven't already: