Within-day gas price down 8.00 pence at 18.50 pence per therm by 1427 GMT.

This is a 30pc drop from Friday's close and the lowest level in nearly 10 years, according to Refinitiv Eikon data.

Day-ahead price down 4.20 p to 21.50 p/therm, falling by more than 16pcpc from Friday to a three-year low.

The October contract down 2.10 p at 30.90 p/therm.

UK gas system's oversupply reduced to 12.6 million cubic metres (mcm) in the afternoon from 41.3 mcm in the morning, National Grid data showed, but prices continued to fall throughout the day.

Increased supply from Norway, a rise in liquefied natural gas (LNG) send-out and lower than expected gas-for-power demand caused the UK system oversupply, resulting in the price drop.

However, in the first trading session in September the pressure of full gas storages across Europe has become more evident as well.

"We are now seeing the impact of not enough storage capacity left," a gas trader said.

UK day-ahead is also not low enough to incentivise an increase in flows from Britain to the continent.

Britain's exports to the continent via the Interconnector UK pipeline were expected to be 10 mcm lower than on Friday.

Britain's gas imports from Norway are up by 14 mcm to 42 mcm/day compared to Friday's imports, Norwegian operator Gassco data showed.

LNG send-out from the South Hook terminal is at around 20 mcm on Monday, a 10 mcm rise from Friday, National Grid data showed.

The Al Ghuwairiya tanker delivered a Qatari cargo at the terminal on Sunday, with Qatari tanker the Al Mafyar expected this week.

Wind generation is expected to be healthy, with wind farms operating at 9.1 gigawatts (GW) of 12.1 GW of available capacity on Monday, Elexon data showed.

On Tuesday, wind generation is predicted to slip to 8.7 GW.

Gas-for-power demand is down by 12 mcm on Monday from previous expectations and is seen down by 8 mcm on Tuesday, Refinitiv data showed.

Day-ahead price on the Dutch TTF hub fell by 0.93 euro per megawatt hour (MWh) to 8.07 euros/MWh.

The TTF October gas price was down 0.88 euro at 11.90 euros/MWh.

Bearish carbon and oil prices also contributed to the fall in the gas contracts.

The benchmark Dec-19 EU carbon contract was down 1.30 euros at 25.02 euros per tonne.

Brent crude slipped 55 cents to $58.70 a barrel after new tariffs imposed by the United States and China came into force.