I am having issues with my local building control in relation to a replacement staircase.

The property is Georgian built circa 1820s and is a very small terrace house in central London.

The original staircase was destroyed by fire in the 1980s (a great shame) but was replaced by a staircase of identical pitch (45 degrees) but in a mirror image configuration.

I now wish to put back in a replica of the original (and restore the original "mirror image" configuration), as part of larger renovations to the property. (Luckily our neighbours still have an original staircase for us to design the replica from).

Now my question is this: our current stairs have a pitch of 45 degs, the proposed replica original stairs have a pich of 45 degrees.

Building control are saying that because I am replacing stairs, they are treated as new and therefore must conform to new build requirements of a max incline of 42 degrees. Trouble is, my architect is struggling to make a lesser pitch fit.

Having read reg 4(2) of the Building regulations, am I right in saying that because, in relation to the pitch, the building work is no more unsatisfactory than before, I should be allowed to retain a 45 degree pitch?