Worcester 20 25 boiler lockout after powercut?

We had a power cut during the night last night, and today have woken to find the boiler on lockout.

Have reset the lockout button a number of times but after about 15-20 seconds of running it locks out again,

I have tried bleeding the fuel system dont think that is the problem, any ideas? plenty of oil in the tank.

James Tucker
February 2011