Phil, you're not the only one to think that so I've done quite a bit of reading on this and it is another one of those grey areas I think.
So from the Guidance on FIrearms licensing there is this:
Antiques
2.40 The provisions of the 1968 Act do not apply to antique firearms kept as curiosities or
ornaments (section 58(2)). There are therefore two key issues: whether a firearm is
legitimately an antique and whether it is to be sold, transferred, purchased, acquired,
or possessed as a curiosity or ornament. The word ‘antique’ and the phrase ‘curiosity
or ornament’ are not defined in law. However, detailed guidance on what should be
regarded as an antique firearm for firearms licensing purposes can be found in Chapter
8. The person in possession of a particular firearm should be able to demonstrate to the
satisfaction of the chief officer of police that it can be treated as an antique for certification
purposes, although it would be for the prosecution to prove otherwise in the event of
the matter coming to court. Evidence of antique status may include an indication of date
of manufacture, details of technical obsolescence, a lack of commercial availability of
suitable ammunition, or a written opinion by an accredited expert. If there is any indication
that a firearm is to be used (that is, not held purely as a curiosity or ornament), it should
not be regarded as an antique firearm for the purposes of the Firearms Acts and normal
certification procedures apply.
This part of it suggests that if it's just an ornament and an antique (which it is) then I can own it no problem.
If on the other hand if it is a starting cannon currently in use then I would need a license. From what I understand it is not really a starting cannon as it does not use blank 10 gauge cartridges like ones I've seen fired to start yacht races.It does not have a breach and cannot be fired via cord to release the firing pin. It really is just an old bit of cast iron.
So to buy BP I definitely need an acquire, to fire this thing I'm not entirely sure as it would not be firing a projectile and is not classed as a shotgun or a pistol.
Being frank, if I wanted to use it as a signalling cannon then I think the license would be needed. For keeping at home for the odd pyro effect, I'm not sure the law would be applied, I certainly don't think charging it with 10g of home made BP would warrant a prosecution or in the public interest.
Of course, I shall be keeping this as an ornament until a time when I know for sure :-) Maybe after the new legislation goes through it will be simpler !!!
I'd suggest trying it with 3 to 5 grams first and not exceeding 10. Use a wad made from a circle of corrugated cardboard a little bigger than the bore, which you ram down with a wood dowel - snip round the edges so it folds into a cup. Wrap the powder in a twist of tissue paper for the best results with a small load. It keeps it together and away from the cold metal walls, and the fire propagates faster.
