Having removed some old plaster to sort out a damp problem, I've found the original fireplace with an arch rather than a lintel. The mortar is generally in good condition. Is the arch still going to be strong enough to support the chimney if I removed the smaller fireplace that was added? It's 1117mm wide between the original brick pillars.
There has also been some rising damp with significant salt deposits over the years as seen in image 3, which I was surprised at with it being an internal wall. I could inject some chemical dpc but how do I stop the damp rising through the first brick?