ANOTHER four-day week — we have four of them in a month and a half. Soon we can take a day off to mark Edward Heath's sec- ularisation of Whit Monday, and another for Michael Foot's socialisation of May Day. I had thought of writing this column at four-fifths of its normal length, to show sol- idarity. Looking round, though, I see soli- darity crumbling among businesses which (like Marks & Spencer) see no reason to shut up shop because of some obscure pro- vision in an Act of Parliament concerned with bills of exchange. I wonder how long the City will observe this obsolete custom which, if it were a contract, would be struck down by the courts as being in restraint of trade. The City sets out its stall as an inter- national marketplace, and should be ready for business when its customers are. Even the bill market, Act or no Act, could adjust. Gone are the billbroker's hours of the old City — starting at 11 o'clock with a smoked salmon sandwich and large gin and tonic (staple breakfast of Arthur Trinder at Union Discount) and ending with a dash for the 3.28 home to Haslemere.