Trying to install Ubuntu on a newly set up LVM2 disk with a Bios_grub partition. Grub won't install.

[Richard Downing]

I deleted all partitions of the disk.
Set up a new GPT partition table.
Set up a new Bios_Grub partition of 1MiB.
Created a LVM2 partition for the rest of the disk (250MB)
Ran pvcreate, vgcreate, and lvcreate to make an LVM2 partition for Ubuntu of 50MiB.
Booted the liveCD for Ubuntu 18.04.
Ran install giving only the LVM2 partition as / (ticked the format box).
Install fails to install grub. The OS is installed on the LVM2 partition.

This is a second attempt, first attempt was onto an SSD with an MBR partition table. Failed in the same place.

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: ubiquity 18.04.14
ProcVersionSignature: Ubuntu 4.15.0-20.21-generic 4.15.17
Uname: Linux 4.15.0-20-generic x86_64
ApportVersion: 2.20.9-0ubuntu7
Architecture: amd64
CasperVersion: 1.394
Date: Mon May 7 13:33:00 2018
InstallCmdLine: BOOT_IMAGE=/casper/vmlinuz file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash ---
LiveMediaBuild: Ubuntu 18.04 LTS "Bionic Beaver" - Release amd64 (20180426)
SourcePackage: grub-installer
UpgradeStatus: No upgrade log present (probably fresh install)