This seems to be caused by having virtualization enabled in the BIOS and then enabling the Hyper-V role. Going into the BIOS and disabling virtualization allows the machine to reboot, and if I remove Hyper-V using powershell, I can then go and re-enable virtualization again.

I have installed the latest BIOS as it cryptically says it fixes an issue where a machine can get stuck on the Dell logo, but this was not the case for this particular issue.