Dame Helen Mirren has revealed her Italian olive grove at the home where she spends four months a year is under threat from a deadly plant disease as she warns British holidaymakers not to bring plants back from abroad.

The actress has joined forces with the Royal Horticultural Society in a campaign to stop the spread of the disease Xylella fastidiosa.

Mrs Mirren has a home in Puglia, where many of the olive trees, which are up to 2,000 years old, have been ravaged by the fast-spreading bacteria.

Her 80 olive trees have so far been unaffected by the disease, but they are at imminent risk as the disease spreads so quickly and so easily.

Dame Helen Mirren said: “I have witnessed first-hand the destruction that Xylella causes in Puglia, Italy – devastating almost overnight countless centuries-old olive trees in the businesses and communities that have long relied on them.

"Preventing Xylella’s spread is a priority and something that UK holidaymakers can support by simply avoiding bringing plants back from abroad that may be harbouring the bacterium.

“Our gardens and green spaces are vital for people and the planet and a failure to act could mean the landscapes that define us could be irreversibly changed. We desperately need more scientific research and support to ensure we can protect the historic Italian landscape and our British gardens and natural habitats for the future.”