
Do you think replace the who leaded glass unit?I’d contact a lead glass specialist.
I doubt it would cost much and if that’s a front door, they could suggest a reinforced glass backing for the door
I thought about this. Call me a traditionalist but I quite like the old look.Replace with double glazed lead decorated single pane .

Stronger and adds insulation.I thought about this. Call me a traditionalist but I quite like the old look.
Why would you favour double glazing?
So from the outside of the door you have the leaded trational glass, then a spacer, the security glass (single pane), then the glazing beading to hold it all together?Leaded windows can be pushed in to gain entry.
A lot of people fit an internal second pane, not double glazed. They use laminated glass, which is two layers of glass sandwiched with plastic film. That’s fitted to a frame screwed to the inside of the door.
I feel the whole door is solid wood and has gaps so the insulation of a small window is neither here or there.Stronger and adds insulation.

The metal bars are just screwed in. Ideally I would like to remove.Actually, it looks like you already have metal (?) bars on the inside.
I assumed that you wanted to retain the original glass detail.
Any local double glazing specialist can make a replacement, complete with leaded effect.
Or a company that specialises in leadwork (my local one did the Harry Potter windows) could fix th original IF the glass pattern is available or make a replacement with similar.
I’d contact a lead glass specialist.
I doubt it would cost much and if that’s a front door, they could suggest a reinforced glass backing for the door
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