Gas Cooker thermocouple replacement

[WSB]

My less than 1 year old gas cooker now has intermittent problems lighting a gas hob. Namely, it goes out shortly after starting and is getting worse.
It's still under warranty, so have an engineer coming round.
Assuming it's the thermocouple, was just wondering whether he'll need to switch off the gas supply, and hence I'll need to restart the boiler or whether the job of changing the thermocouple doesn't require the gas to be turned off?

Also, is it normal for a thermocouple on a gas to go wrong so quickly?

And if there's anything I can do to avoid similar going wrong in future?

Thanks in advance

 

[cross thread]

Any new hob should have a gas isolation tap inline.Have you checked the burner cap for muck

 

[WSB]

Thanks, hopefully they'll be able to just switch that off.
All clean.
Just surprised it's gone that quickly