Black spots on underside of Bay leaves

Can anyone identify these black spots on the underside of my bay leaf plant
and how it can be treated.
They appear mainly on the underside and very little on top of the leaves.
Under a magnifying glass it appears like some sort of fungus, definately not an insect.
About 50 percent of the leaves are covered with these spots.
Thanking you kindly.

 

Googled my bay leaf problem and came across this old post with no reply.
The one with the problem is in a container.
I have a healthy one in the ground that I use for cooking so any solutions don't need to be edible!

 

My neighbour has a massive bay tree growing in her garden which she kindly lets me pick from. I collected some leaves a few days ago and noticed similar markings on some of the leaves of her tree. It may be a fungi which particularly likes bay. No idea what.

 

Here's mine. I wonder if it would be worth picking off the affected leaves - a BIG job.
It's in a slightly shadier spot than is ideal so it could definitely be a fungus.

 

I suspect it's the older leaves being attacked by a fungus. Probably won't bother you if cooked and eaten, but I just pick unaffected leaves and leave the spotty ones.

 

I have a huge unaffected bay that I use for cooking - the leaves that the sparrows haven't whitewashed.