Joan Parker-Grennan sued Camelot after a system error lead for her to be told she had won £1 million.

But the company disputes her claim and says it is only liable to pay £10.

Mrs Parker-Grennan had played online after buying an Instant Win Game ticket on August 25, 2015.

Camelot says the premise of the game was that if a number in the ‘your numbers’ section of the screen matched one in the winning numbers section, the two matching numbers would turn white, indicating that the player had won the prize.

The company says that ‘at the point’ Mrs Parker-Grennan bought her ticket, its computer system predetermined her prize to be £10.

Two numbers with a designated prize of £10 were highlighted on Mrs Parker-Grennan’s screen with a message saying: ‘Congratulations, you have won £10.’

But Mr Justice Jay was told two other matching numbers – with a designated prize of £1 million – also appeared due to a technical issue.

The court heard between August 25 and 26 2015 there had been a ‘technical issue’ which could result in ‘different graphical animations’ being displayed on some players’ screens.

Barrister Philip Hinks, leading Camelot’s legal team, argued that the operator was only liable to pay the ‘outcome of the ticket as predetermined’ by Camelot’s computer system.

He said that was £10, not £1 million.

Barrister James Couser, representing Mrs Parker-Grennan, said there was ‘no real prospect of the claim being successfully defended’.

He told the judge: ‘The defendant says that the terms mean that the claimant is bound by what it intended the outcome of the game to have been, despite the fact that was not what the game was programmed to do accorded with what the relevant contractual term said it could do.’