Where a beneficial owner cannot be determined so therefore the beneficial owner is determined to be the board of directors. Is it possible to nominate one person on the board as the beneficial owner for the beneficial ownership register?

No the beneficial ownership register requires all persons on the board of the directors of the company to be named in the beneficial ownership register. You cannot pick and choose. The European Union (Anti-Money Laundering: Beneficial Ownership of Corporate Entities) Regulations 2016 refers.