This isn't particularly a handbell-related topic, although it is prompted by ringing (on handbells) the major, royal and maximus versions of the methods that I discussed in the previous article: Cambridge, Yorkshire, Lincolnshire and especially Bristol. One of the things I find difficult about Bristol Royal and Maximus is the wrong dodges. Part of the reason for finding them difficult is that they don't occur in Bristol Major, and that in turn is essentially the reason why Bristol Royal and Maximus are not extensions of Bristol Major.
What? Bristol Royal and Maximus aren't extensions of Bristol Major? How can that be, when they have the same name? Well, the rules (or "decisions" if you want to be finicky, but I'll call them rules) for method extension have changed from time to time over the years. As I understand it, according to the current rules, Bristol Royal is not an extension of Bristol Major, although Bristol Maximus (and all the subsequent stages at which it has been named) is an extension of Bristol Royal. As an aside, Clyde and Strathclyde are extensions of Glasgow, although I suppose the different names are because they were named at a time when the rules did not consider them to be extensions of Glasgow.
I have never really digested the details of the extension rules, so I decided to look them up and see whether I could understand the Bristol situation. The rules are described as part of the Framework for Method Ringing, and although complex, they are explained clearly with a detailed example. I won't go through everything here, but to see why Bristol Royal isn't an extension of Bristol Major, we just need to appreciate that each section (i.e. the block of place notations while the treble dodges in a certain position) in an extension is based on a section in the original method, possibly with places moved upwards (away from the front) or downwards (away from the back). Crucially the whole section is treated in the same way, which means that a symmetrical section in the original method can never give rise to an asymmetrical section in the extension. Bristol Major consists entirely of symmetrical sections (the place notation for half a lead is x58x14.58x58.36.14x14.58x14x18) but Bristol Royal has the asymmetrical section 14x70 when the treble is in 5-6 (the place notation for half a lead is x50x14.50x50.36.14x70.58.16x16.70x16x10). Therefore the extension rules can't produce Bristol Royal from Bristol Major.
What about the extension from Royal to Maximus? The place notation of Bristol Maximus is x5Tx14.5Tx5T.36.14x7T.58.16x9T.70.18x18.9Tx18x1T. The 14x7T and 16x9T sections both come from the 14x70 section in Bristol Royal, in the latter case shifted up by two places. The 18 notations come from the 16 notations in royal, shifted up by two places. The 9T is the same as 70 when viewed from the back.
Coming back to the line, the wrong dodges are caused by the asymmetrical sections, so the unjustified appearance of the asymmetrical sections in Bristol Royal corresponds to the unjustified appearance of wrong dodges.
By the way, the rules for extension say nothing about place bell order. It's true that the place bell orders of Bristol Major (8642357), Royal (097532468) and Maximus (T728E540936) look very different, but actually they are all -8, meaning that they are equivalent to the opposite of 8 leads of Plain Bob (Plain Bob itself is +1). Similarly the place bell orders of Glasgow, Clyde and Strathclyde look very different, but they are all the opposite of the corresponding Bristol place bell order, i.e. +8.
So, are there any extensions of Bristol according to the rules? Using Composition Library it's easy to check, by looking at the "related methods" section of Bristol Major. There is one extension to royal, which is this method that has a three-lead course. More interestingly, Smallbrook Surprise Maximus is an extension of Bristol Major. Here's a diagram from ringing.org.
How does it look? Lots of points - more than in Bristol, because there are sets on the front four and the back four as the treble goes through 5-6 and 7-8. So potentially more landmarks. Some extra fishtails, when the treble is in 5-6 and 7-8. These do correspond to Bristol Major, where there are fishtails above the treble's 5-6 dodge, and in Smallbrook these also get reflected into 5-6 when the treble is in 7-8. The grid looks like Bristol when the treble is in the front four or the back four places, and when the treble is in the middle, it looks like Bristol on the front four and the back four with treble bob around the treble. So even without digging into the details of the extension rules, there is some intuitive sense to it. Maybe something to try in the distant future.