This is the chart of long term storage.
The real problems arise whenever either of the safety monitors is breached. Short term storage (LNG mainly) allows the handling of peaks in demand. It can run at about 47 mcm/d for about 3 days. Medium term can run at 28 mcm/d for (now) 15 days and long term can run (now) for 70 days at 45 mcm/d.
The safety monitors exist at 22% of LTS, 13% of MTS and 22% of STS to ensure that if the system cannot cope with demand that it shuts down sensibly. If domestic customers were ever to be cut off that would
a) Cause major hardship ... and
b) Take some time to reverse as you cannot just switch the gas back on again
(pilot lights and all that).
Hence the system is designed to ensure that whatever happens we should not have to do that.
This means (see earlier) that big consumers are cut off first (such as the electricity generators).
The real problem is that during Winter although we can use LTS for 70 days we should not be having to use it now.
My guess is that yesterday's demand of 373 mcm there will have been some medium term storage used. If it gets colder we could start biting into the short term and that only gives a short period before the safety monitors are breached.
I have put forward some proposals for the government to increase supply, but I think they should be looking beyond the market for mechanisms to reduce demand.