[r-t] Doubles 240s

[John Harrison]

> Don had proposed allowing to null change to enable 240s of Doubles with
> each row at hand and back.

> This is unnecessary. Some years ago, I produced 240s with this property, 
> but using conventional bobs and 123-singles. 

I don't recall him saying it was necessary (but I haven't looked up the
archive).  I thought it was an example of a neat way to do it.  It is
certainly one that might appeal to 'ordinary ringers' because it is simple
to understand and simple to call.

-- 
John Harrison
Website http://jaharrison.me.uk