When forming a UK company you have the option to appoint a company secretary.
UK companies do not need a secretary.
Under the Companies Act 2006 UK companies are not required to appoint a company secretary. When forming a company you only need to appoint one director. In the absence of a company secretary the roles and responsibilities associated with the company secretary fall upon the company director(s).
A company may appoint another company as company secretary.
If required a company can appoint another registered company to act as company secretary. Whilst the company secretary is no longer legally required some organisations may use a corporate entity to act as the company secretary.
Company secretaries can also be directors.
When registering a company you can make one person both a company secretary and a company director. This is quite common with older companies but as the law now means that companies can be formed without a secretary it occurs less frequently.