You will need the Secretary of State's prior approval if your chosen name: -
In the case of any name that requires approval because of the connection it suggests or if it includes certain sensitive words or expressions, you must request the specified Government department or body to indicate whether (and if so why) it has any objection to the proposed name. The application to register a company includes a section requiring you to confirm you have sought the comments of the appropriate body. You must also deliver a copy of any response received and in the case of words, other supporting information with your application. Companies House will then consider whether to approve the name on behalf of the Secretary of State.
These are words and expressions which, when included in a company name, may imply business pre-eminence, a particular status or a specific function. For this reason, you must seek approval of the Secretary of State before the proposed company can be incorporated (or requesting a change to a company's name). The aim is to ensure that the inclusion of the word is justified so that its use in the name does not mislead the public. Companies House administers the approval process on behalf of the Secretary of State.
A complete list of sensitive words, and what you will have to prove in order to have permission to use a sensitive word in the name of your company can be found at Companies House web site.
In order to use a sensitive word in the name of your company, you must supply supporting evidence to Companies House when you apply to have your company incorporated.