4mm or 6mm cable

[Sammw123]

Hi

I am having a job done on my wiring. I have had one electrician say that it is a 4mm cable that needs replacing to a 6mm cable and another electrician say it's a 6mm cable that doesnt need replacing can anyone help as I am now confused who to do the job ?

Thanks

 

[Wilko]

Here’s some cable sizes if you’d like to measure them next time you’re up in your loft