Partitioned disk but Bootcamp problem

I need more space on my Bootcamp partition so I removed it with BootCamp Assistant and checked that the Mac HD was again full size.

Then I ran BootCamp Assistant again and made the partition the size I need.

I had already downloaded the Windows 10 iso, so started the installation. I got as far as inputting the Windows 10 Home and Language before it stopped and failed to install.

When the machine opened again in Mac, I checked the partition size and it had reduced the Storage to the size I'd set.

When I tried to run BootCamp Assistant again, the only option was to put the Mac partition back to its original size.

How do I get to a point where I can install Windows 10 on a Bootcamp partition, please?

(Mac OS High Sierra, v 10.13.6 2017)