It is important to prioritise spending commitments, and in a time of spending cuts this visit represents a series of costs that the taxpayer can't afford to pay. For other events such as football matches the organisation requesting the police presence can pay up to 100% of the policing costs, and in the interests of fairness the church shouldn't be exempt.
The Pope's visit to the UK next year was expected to cost the state £8m, bit Lord Patten revealed today that it could cost £12m. This figure doesn't include policing costs.
Save money by asking the Catholic Church or private contributors to pay for the entire costs of this visit, including a contribution towards policing costs.