The within-day contract  was up 0.60 pence at 52.60 pence per therm at 0915 GMT, while the day-ahead contract  was 0.75 pence higher at 53.30 p/therm.

Demand was forecast at 335.5 million cubic metres (mcm), above the seasonal norm of 304 mcm, while flows were forecast at 331 mcm/day, leaving the system undersupplied by around 6.5 mcm, National Grid data shows.

Consumption is up for the day-ahead contract, but consumption for working days next week is down by 11 mcm/d.

Thomson Reuters analysts see local distribution zone consumption around 25 mcm/day below normal for most of the week.

On the supply side, an outage at the Rough natural gas storage site has reduced withdrawal capacity and is not due to end until 1400 GMT. [GAS/OUT]

Flows from the UK Continental Shelf are still affected by an outage at the Bacton Seal terminal which has reduced its production rate.

Flows to Britain from Norway through the FLAGS and Vesterled pipelines are down by 3 mcm and there are no liquefied natural gas tankers scheduled to arrive in Britain.

Further along the curve, Winter 2017 gas is up by 0.49 pence at 51.25 pence per therm.

"The Prime Minister is due to make a speech on the Brexit plan of action later this morning, which could see some volatility in the value of Sterling and offer the NBP (National Balancing Point) some additional direction," said Andrew Crabtree, pricing and risk analyst at WINGAS UK Limited.

Britain will not seek a Brexit deal that leaves it "half in, half out" of the EU, Prime Minister Theresa May will say on Tuesday in a speech setting out her priorities for divorce talks which indicates she is prepared to leave the single market.

In the Netherlands, the day-ahead gas price at the TTF hub  was up by 0.50 euro at 19.58 euros per MWh.

In the European carbon market, the benchmark Dec. 17 contract  was down by 0.05 euro at 4.75 euros a tonne.

(Reporting by Nina Chestney)