Boiler won't stay alight

I have a really ancient potterton Kingfisher which is overdue for replacement. However that is not due to happen until the spring. Recently it has performed very well but now I have a problem.

The pilot light will stay alight no problem. However as soon as the boiler fires up it runs for about 1 minute and then cuts out with the pilot light having gone out. To my total non technical eye it seems as if the boiler running blows out the pilot!

It had a new thermocouple about 2 months ago.

Any help much appreciated

Your non technical eye could well be smarter than you give it credit for.

Watch the pilot, if you can see it, when the main flames come on. Does the pilot shrink? If so, it needs a bit of a service.

Thanks for that. Yes I can just about see the pilot getting smaller. I have booked a service but the engineer can't come until Friday! Is there anything I can do in the meantime to try and keep it going?

I have cleaned the pilot itself but that has not made any difference.