Such torturous routes were very common last century as the only way in very old city centres (often found in London, Manchester, Leeds, Liverpool & Birmingham) of giving existing landlocked buildings a second MoE & was considered better than nothing, along with hatches and doors in party walls, etc.
However guidance has been set against this sort of thing for a long time and the FP Act guides deprecated them too.
Having said that even current guidance accepts ladders, etc - but only in exceptional circumstances.
ADB
Fixed ladders should not be provided as a means of escape for members of the public. They should only be provided where a conventional stair is impractical, such as for access to plant rooms which are not normally occupied.
DCLG/HO
While not normally acceptable, the use of ladders, floor hatches, wall hatches or window exits may be suitable for small numbers of able-bodied, trained staff in exceptional circumstances. (more or less mirroring the FP Act guide other than a prescriptive number which I believe used to be 5 without digging them out)
So I would ask - who are they expecting the route to be used by?
"signed off under fire regulations" implies, as we don't have fire certificates, that either they are fibbing or the broken building control process has just cracked again if this has been accepted for a normal escape for building occupiers as oppose to a plant room or similar (where they are common)