how do I access my deceased father's icloud account?

For information about how to request access to a deceased family member's Apple accounts, and through this their equipment, click here --> How to request access to a deceased family member's Apple account - Apple Support

It states you need a court order.

Hello ~ This is Apple’s UK document on that matter and you may click on to review or contact Apple for more information…

How to request access to a deceased family member’s Apple account – Apple Support (UK)

Contact Apple for support and service

Good luck and you have my condolences.

~Katana-San~

Note, the link I provided does not have any region forcing set on it. It will render whatever country version you have for the country to which your browser ID is set.

Edit:

I just checked the UK version and it too says:

"For security, Apple requires and verifies legal documentation before we can assist with a deceased person’s account. This generally includes a death certificate, and may also require a court order or other documentation. The requirements vary by country and region. We have great sympathy for surviving family members and try to help with

requests as much and as quickly as possible."