Gardening guru Alan Titchmarsh, 70, returns for a new series of Secrets Of The National Trust.

The green-fingered star tells Sherna Noah about his behind-the-scenes peek at some of Britain's finest historical homes and gardens on the Channel 5 show and the issues he is passionate about.

SECRETS OF THE NATIONAL TRUST IS BACK FOR A FOURTH SERIES. WHY IS IT SUCH A SUCCESS?

It's a wonderful way of looking at things within National Trust properties that you might not usually get to see.

We've got such a rich legacy with these properties. And Secrets goes that little bit deeper. It fascinates me when I'm going around.

ONE EPISODE TELLS THE STORY OF WILLIAM JOHN BANKES, THE 19TH CENTURY OWNER OF KINGSTON LACY, A GRAND MANOR AND ESTATE IN DORSET. HE WAS FORCED INTO EXILE OVER HIS HOMOSEXUALITY?

This was at a time when falling in love with people of the same gender was illegal.

Here's a man who had to leave the country. But they think he came back secretly just to check that all his artwork was being properly displayed.

So we're looking at culture as well as objects.

YOU ARE PASSIONATE ABOUT GARDENING AND GETTING OUTDOORS. IS THERE ENOUGH TIME FOR THIS IN THE SCHOOL CURRICULUM?

The curriculum should cater for several periods each week outdoors. Even in inner city schools you can do it. There are green spaces.

I don't need to spout Latin names at my grandchildren but they adore being outside, whether it's collecting eggs from chickens or picking raspberries or just running around.

They are the future custodians of the landscape. We need to get them familiar with it.

DOES GARDENING HAVE MENTAL HEALTH AS WELL AS PHYSICAL BENEFITS?

It makes me smile when I see something that says GPs are saying that gardening is good for you. Oh really? Tell me something else I don't know!

It's obvious, gardening is therapy.

Instead of just worrying and reading headlines about global warming and climate change and how we're all going to hell in a handcart, we need to get involved.

Most of us have got a patch of ground at the back of our houses where we can make a little difference.

Do it there, grow plants for bees, grow organically, don't use sprays. Bring it back on your little bit and all those little bits will join together.

ARE CHILDREN TOO CLEAN NOW?

Yes! A woman said to me, 'What shall I do about little boy eating soil?' I said, 'Make sure he gets enough!'

How else do you build your antibodies up? They should ban antiseptic wipes. They clog up all our systems and they end up in the oceans. It's dreadful.

These adverts, 'They kill 99.9 of household germs'. Well, not all bacteria is bad. How do you build up resistance?

I'm not saying don't wash your hands when you've been to the loo! But just be a bit more realistic.

DO YOU MISS CHELSEA FLOWER SHOW AND GARDENERS' WORLD WHICH YOU PRESENTED FOR MANY YEARS?

I had a lovely time doing it and I'm all for keeping fresh and doing different things but I sort of (feel I) did it.

I would never complain about anything I used to do and don't do now. I've got enough on.

THE ALAN TITCHMARSH SHOW WAS A TV STAPLE. WOULD YOU LIKE TO DO ANOTHER CHAT SHOW?

I would love to ... although not every day. I was doing Monday to Friday. But one a week, I'd do it until I hopped the twig!

WHAT ABOUT GROUND FORCE, WHICH LAUNCHED YOUR NAME?

It's always on! My wife turned it on the other night. I thought, 'Oh crumbs. I was about 12. I looked at it and thought, 'Was that really me?'

HAVE YOU EVER BEEN TEMPTED TO HAVE A NIP OR TUCK?

No, I leave it to God. It will go wrong, I'd go lopsided.

You watch enough disasters and think, 'Why did you do that?' You have one bit nipped in and the other bit collapses.

It's like cutting hair. You take too much off one side and you go on until you look grotesque.

I look at people like Dame Judi Dench and Dame Maggie Smith and they haven't had anything done. They've still got sparkle.

It's what's inside, it's heart as much as anything.

YOU WERE VOTED SECOND SEXIEST MAN, NARROWLY BEATEN BY GEORGE CLOONEY. DO YOU ENJOY YOUR SEXY STATUS?

I doubt that I would hold the record now - more people have come along!

But I'm very grateful to be mentioned in the same paragraph as George Clooney.

YOU ARE PASSIONATE ABOUT EATING SEASONALLY AND ENJOYING LOCAL FOOD. DO YOU EVER BUY A READY MEAL?

Yes, I'm human! But I know which ones I like buying and I have a wife who's a wonderful cook.

I'm not saying I'm a saint. I struggle like everybody else. But we do not buy raspberries in February which have been flown in.

Mrs T is the cook and the grower. Mind you, I do a mean cooked breakfast!

*Secrets Of The National Trust With Alan Titchmarsh is on Channel 5 now