Extent of Bristol Surprise Royal

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In June 2018, after some weeks of writing out figures on many sheets of paper, I managed to compose the exent of Bristol Surprise Royal - 3628800 changes.

The composition is here:

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An article about its construction was published in the Ringing World October 2018.

An extent of Bristol Royal is possible for the same reason that extents of Cambridge S Minor and scores of other TD Minor methods are possible. There is no in-course falseness at all, so a mutually true set of in-course courses can be put together to make an extent. Though Bristol Major has no in-course falseness when the tenors are kept together, there is still out-of-course falseness that can be rung in reverse when the tenors are split - even when no singles have been called.

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But this problem does not occur for Bristol Royal, so the secret is to keep the bells in-course and not call any singles. For a bobs-only composition, irregular q-sets have to be used to gather an even number of courses rather than an odd number (the same technique used to compose bobs-only extents of Cambridge Minor and Bob Triples.)

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It was more interesting to compose an extent of Bristol Royal, being a Treble Dodging method, and I would never have bothered to compose an extent of Bob Royal. However, an exact two-part extent of Bob Royal with only 2 singles is certainly possible, and is directly analogous to 720s of Bob Minor with only two singles.

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My composition is not the longest peal ever composed, as at least one extent of Maximus has been published. However, my composition is possibly the first extent of Royal to be composed.

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Having composed the extent, I then needed to find a program that could actually prove it! JSProve - the excellent website made available by James Holdsworth and Paul Brook - came to the rescue, and confirmed that my 3628800 was true. Here is the screenshot I took of the result: