The 'Alan Titchmarsh Effect' is giving the Chelsea Flower Show a massive boost, and according to national newspaper reports, tickets for world-famous event starting on May 20 are now being sold on the black market for over £550.

Titchmarsh is designing his first Chelsea garden since 1985 after losing the frontman role for the BBC's coverage of the show. 

All 161,000 tickets to the event have already gone, the  second-fastest sell-out in its history. Only last year’s centenary show, when Prince Harry was involved in a show garden, sold out slightly quicker.

And organisers from the Royal Horticultural Society say that the ‘Titchmarsh effect’ had given the show a big boost.

RHS spokesperson Hayley Monckton said: "Alan Titchmarsh is this year’s Prince Harry for us. He is one of Britain’s best loved gardeners and everyone is very excited about seeing his garden."

His Chelsea garden ‘From the Moors to the Sea’ charting his journey from his native Yorkshire to the Isle of Wight, where he has a holiday home, is his first since winning a gold medal in 1985.

But according to a report in the Daily Mail, the ‘Titchmarsh effect’ has left  gardening fans facing online prices of up to 25 times the face value of the cheapest £23 tickets.

RHS director general Sue Biggs said: "Alan is one of the most powerful forces in horticulture, reaching out to and promoting gardening to millions of people.

"He has also been one of the biggest supporters of the RHS and, as this garden demonstrates, continues to generously support and promote horticultural campaigns that transform lives and reinforce our great position as a nation of gardeners."

The RHS is urging gardeners not to buy tickets from touts and warning anyone with tickets that turn out to be fakes will be denied entry.