It is plainly absurd to fine MPs retrospectively for expenses that were approved in good faith years ago, and if Sir Thomas Legg thinks it is reasonable to do so merely to satisfy the voices of the mob, then he has a very odd sense of natural justice. Natural justice is not what appears in a Telegraph or Mail editorial. But those who can afford £1.3 million flats in central London clearly don't need to worry about trifles like expenses.
And the real reason why these allowances have been allowed to grow as they have is in danger of being forgotten in the ensuing controversy. MPs allowances - as with those for peers incidentally - have always been intended to supplement their salaries (or substitute for them) by covering all the additional costs they incur as a result of living in London as an MP in addition to any constituency home (until 2004, ministers were required to designate London their first home, a fact conveneniently forgotten is the attacks on Jacqui Smith).
That's why many tended to claim close to the full housing allowance, even if it involved mortgage interest subsidies. In that context, the Legg letters may politically require paybacks, but far more important is the establishment of a much clearer system of MPs pay and expenses (which are not the same thing as allowances).
So, MPs should have an overnight accommodation and subsistence allowance - say £200 on days that Parliament sits - that would allow them to stay at a reasonable 3* or 4* hotel in central London - the Commons can block book rooms to get good deals - or accommodation in apartment blocks wholly leased by the Palace of Westminster. The hotel/subsistence allowance should not exceed £200 a day. Mortgage costs would not be paid.
Any cleaning or other such costs would not be handled by MPs but dealt with by officials (or covered in hotel bills). Train fares (normally second class) should be paid with rail warrants and mileage costs covered for constituency business. Otherwise any expenses would be directly related to official business and suitably receipted.
The sooner such a system gets established the better for MPs and the better for their reputation.