well thats not what the NG were saying last month.
That depends on how you read "As importantly, the current network cannot handle the extra load required."
The much-quoted factoid is that the Grid cannot cope with the draw imposed by domestic EV charging and you will get local substation meltdowns. This is largely incorrect. The Grid has a capacity of ~80GW. Peak draw in 2005 was 63GW, peak draw in the last two years has been ~47GW thanks to massively improved domestic and industrial energy efficiency, plus growth in embedded generation (mostly domestic solar).1 We're nowhere near the actual transmission capacity of the grid (notwithstanding local substations which may be more heavily loaded than others).
The NG have repeatedly stated that the Grid has enough capacity to charge EVs, and anywhere that doesn't will be upgraded over the next 10-15years as EVs become more common and ICE is phased out. It's not as though anyone is flipping a switch. It's a gradual growth and they have time to upgrade substations and distribution nodes as demand rises and individual town or neighbourhood capacity is reached.
Outright Generating Capacity is a different kettle of fish, and if we read "grid capacity" as meaning generating capacity then there is more of an issue. On average, we currently have a comfortable overhead for overnight charging. Winter peaks are starting to cause issues as we have been busy decommissioning coal plants and other dispatch-able generators. Realistically we will need more, but that's at least 10years away. Improved storage (probably pumped hydro) will allow us to store excess wind rather than turning down dispatch-able generators when the wind blows, storing that power for peak periods. We're not currently generating as much as we could because we have nowhere to put the excess power at slack periods. Hinckley Point C will also help.
The fact that NG have had issues with peak winter demand in the past couple of years should not be taken as an indication that we fundamentally can't charge EVs or are running out of power. Most of those problems can actually be met with storage rather than outright additional generation (although we shall require both).
It is also worth noting that the often quoted figures for car energy usage now look rather high. UK Road usage declined 22% last year. Obviously it will bounce back but it seems likely that there will be significantly increased WFH going forward, along with modal shift with increased local rail coming online over the next decade.
1. For instance, as a kid our home would regularly pull 1.5kW of an evening via 100W lightbulbs, the CRT telly and Pentium 4 space-heater. These days we're struggling to crack 200W with two adults working from home with 27" monitors. If I turn on every bulb in the house the lighting draw won't exceed 100W. The compressor in the fridge is far more efficient than those of the 80s, etc, etc.