THE royal family's commercial property empire has delivered a record £304.1 million to Treasury coffers and seen the value of its portfolio rise 9.7% to £12 billion.

The Crown Estate, which owns large swathes of land and property across Britain, said its income rose 6.7% last year as it reaped the benefits of a regeneration plan and its offshore wind assets.

Chief executive Alison Nimmo said: "We have outperformed the market and benefited from our team's expertise and disciplined commitment to our core sectors.

"With markets continuing to be fully priced, we have secured our long-term sustainable growth through the active management of world-class office and retail destinations, the strength and timing of the largest development pipeline in our history, together with the UK's world leading position in offshore wind."

The Crown Estate owns Regent Street and much of St James's in central London, Windsor Great Park, large amounts of rural farmland and the entire UK seabed. It leases the seabed to offshore wind farms, and the amount generated from these operations rose nearly 20% to £22.9 million over the year.

A £1.5 billion regeneration of Regent Street and St James's helped the group let out all of its West End shops.

Meanwhile, the Prince of Wales's income from his private estate of lands, buildings and financial investments has increased to £20.5 million, according to accounts.

Charles saw a 3.1% rise in the year to March in his funds from the Duchy of Cornwall, which owns assets like London's Oval cricket ground and has the Isles of Scilly in its portfolio.

The heir to the throne pulled in £20.467 million from the Duchy, up more than £600,000, and also received £1.4 million in funding from the Sovereign Grant and government departments during the period.

His tax bill was up more than £500,000 to just over £5 million, while other expenses, including the cost of official work by the Duke and Duchess of Cambridge and Prince Harry, rose to £3.2 million, an increase of almost 10% on the previous year.

Charles pays income tax voluntarily on the surplus of the Duchy of Cornwall, applying normal income tax rules and at the 45% rate, and pays income tax on all other income and capital gains tax like any private individual.

The 75th anniversary of the Battle of Britain, the 70th anniversary of VJ Day and the bicentenary of the Battle of Waterloo were among the key celebrations and anniversaries attended by senior members of the Royal Family.

Official expenditure for Charles and the Duchess of Cornwall came to £10.5 million, a fall of more than £1 million. Official travel by air and rail fell by more than half from £1.5 million to £658,000.

Greenhouse gas emissions, which could be linked to Charles's household, fell to 1,266 tonnes from 1,578 tonnes for the same period a year earlier.

Emissions from official overseas travel amounted to 1,101 tonnes in 2016, down from 1,833 tonnes, while 2,257 tonnes were recorded from Home Farm, up from 2,124.

Charles and Camilla carried out 158 overseas engagements across 11 countries including Ireland, Croatia and Serbia.

Closer to home they visited 41 counties and 89 cities, towns and villages in the UK in work in support of the Queen.