The Serjeant at Arms is always consulted regarding criminal investigations involving hon. Members which may involve police officers entering the parliamentary estate. The Metropolitan police acts as a conduit for matters involving other forces. In general, such issues are dealt with away from the parliamentary estate. The conduct of the inquiry would be a matter for the investigating force, however, the Serjeant is always concerned to ensure that no action should be taken within the estate which would be detrimental to the status and reputation of Parliament. No formal guidance exists but Mr. Speaker or the Clerk of the House would be consulted in exceptional circumstances.