It is a propaganda point for AQ to link attacks on the UK with Iraq and hence that link will be made. Strategically, that isn't necessarily why they are doing it though, but they'll most certainly *say* that's why they are doing it.
And it must be exposed for the lie it is. They tailor their excuses for each act of barbarism to suit the arguments of critics. They understand that western culture tends to question itself. To ask if we could have prevented this, rather than to put blame where it is only due. They use this to weaken us, as they prepare further acts of terror.
They alone bear the blood for the innocents in the streets. They alone will burn in Hell for this.