Chef - splitting between tax years would make little difference for such a huge amount.
We also don't know that he'll be paying tax on it. Presumably he'll be using VCTs or something to avoid/defer the tax. Such arrangements can always be changed by the fickle and interfering hand of Gordon Brown, so might be best entered into now rather than waiting.
If there's a bad trading statement in the near future, Gall knows he'll be facing investigation for the timing of his sale. However ineffectual the regulators are, I can't believe he'd want to risk the bad publicity and inconvenience. Besides which, we know from the deals announced that trading's strong. Nothing to worry about IMHO.