On April 28, Pfizer announced a possible offer to buy AstraZeneca, presumably having thought an announcement was required by rule 2.2 of the Takeover Code. The result is that, under the relatively new ‘put up or shut up’ rule now embodied in rule 2.5 of the Code, Pfizer has until 5 o’clock on May 26 – the 28th day after its announcement – in which to make a firm offer.








