Lintel below a lintel - opening a fireplace

Afternoon guys,

I am opening up an old chimney breast that was blocked up years ago. The reason is twofold - ventilation (it wasnt vented!) And decoration.

The new opening will be 400mm wide x 600mm high which is smaller than the original so I'm only knocking out 'infill bricks' and not any of the original chimney structure. This means my new opening is approx 2 courses below the original lintel.

Here's the question - do I need a new lintel below the original? From what I can tell it will only be holding up two bricks.

I dont want to cut corners but also I dont want to create extra work for myself. As the bricks arent loose do you think a decent bit of strong render will do?

I should clarify - this will be a decorative fireplace only and is not intended to be functional. In fact hidden behind I will box it out and add a vent.

Any advice here would be really appreciated.

Thanks in advance! R

(Pic shows the work 90% done, just top right to tidy up and bottom course to knock out)

Updated pic ...

Raised the opening another course - existing lintel is some sort of metal strip, likely iron I think.

If it’s only decorative you could use a wooden lintel but your brick course needs support