The Staffordshire Hoard of Anglo-Saxon gold is expected to be valued at around £3 million this week – almost double the amount of the most expensive ancient treasure previously found in the UK.

Finder Terry Herbert, from Burntwood, and land owner Fred Johnson, of Brownhills, can expect to eventually receive tax-free windfalls of about £1.5m each.

It has also emerged that the find of gold and silver from the farmer’s field is bigger than first announced. There are 1,800 individual items – 300 more than initially revealed.

The Government’s treasure valuation committee will meet on Wednesday to consider the advice of a panel of independent experts and put a value on the artefacts.

Unemployed Mr Herbert, aged 55, of Scott Way, stumbled across the hoard in July.

Mr Herbert, who is on medication for a heart condition, has previously said he plans to buy a bungalow with his share, but said yesterday he was still thinking about what to do with the money. “I expect that any money I get will be invested,” he said.

Mr Johnson, aged 65, of Lichfield Road, added: “Whatever I get I shall take advice from an accountant. I shall not be going out to buy a new Ferrari,” he said.

The hoard artefacts contain more than 5kg of gold – three times the amount found in 1939 at the Sutton Hoo burial site in Suffolk – and 2.5kg of silver.