This comes as a bit of a surprise. According to the announcement, Managing Director Gerard Dyson has resigned. Now, we're left to read between the lines as to why—possibly, the board is implying that it's to save cash.
Dyson is a major shareholder and will remain on the board in a non-executive role. Perhaps I missed something (though I don’t believe I did), but for a CEO of a public company to resign without a clear explanation doesn’t seem sufficient to me.