Right. However, if doing stepped flashing, you're likely to have to patch
surrounding pointing also. How well does lead sealant match this?
Otherwise, it seems you'll still have to knock up some mortar anyway?

Being dark grey, it matches well to the lead. I imagine the match to your
average mortar would be appalling!

In my case, I didn't need to touch the pointing. I needed a angle grinder to
shift it, it was so hard and certainly didn't remove any more than I needed
to.

Christian.