To all those saying "he should have landed back immediately", nobody has mentioned landing distance. Guernsey is SHORT ! only 1,700m.
With the loss of an engine - and who knows what collateral damage - did they have all their stopping systems available? Wheel brakes, hydraulics, spoilers etc? They obviously only had reverse pitch available on one engine, and depending on the weather and conditions, asymmetric reverse pitch might have been a no-no.
We don't know do we? , but there is a strong possibility that their landing performance might have been compromised. So they opted for an airport with a longer runway. Given that you have left Guernsey and are flying north, it makes no sense to turn south towards France, and Jersey is also quite short, so that leaves you with EGKK, EGLL, and EGSS with long runways in the south of the UK. If you are near the south coast of the UK by the time you have contained the problem and run all the appropriate checklists, the obvious thought would be EGKK. But again, I don't know what the weather was, or what the approach aid servicability was that day. There might have been a very good reason why EGKK was not the most suitable diversion airfield - and forget about EGLL unless you have an uncontained fire !
As far as I am aware, nobody with a current ATPL, let alone a Captains rating or even a type rating is a staff writer on the Daily Mail, or the Torygraph. So what the hell do they know about landing a Dash 8 - Q400 with an engine failure?
Gentlemen of the press if you are reading this: Please would you show more respect to your own profession by at least thoroughly researching incidents before pronouncing on the actions of actual professionals who are doing a highly skilled job that you have no experience of.