R v Chaytor and others [2010] UKSC 52, [2010] All ER (D) 19 (Dec)
(i) The submitting of claims by MPs for allowances and expenses did not form part of, nor was it incidental to, the core or essential business of Parliament, which consisted of collective deliberation and decision making. The submission of claims was an activity which was an incident of the administration of Parliament; it was not part of the proceedings in Parliament.
(ii) The House of Commons did not assert an exclusive jurisdiction to deal with criminal conduct, even where that related to or interfered with proceedings in committee or in the House. Where it was considered appropriate the police would be invited to intervene with a view to prosecution in the courts. Furthermore, criminal proceedings were unlikely to be possible without the cooperation of Parliament. Before a prosecution could take place it was necessary to investigate the facts and obtain evidence. Parliament by legislation and by administrative changes had to a large extent relinquished any claim to have exclusive cognisance of the administrative business of the two
