Williams says he is returning after four years away because he wants to introduce his son and grandson to the show. Medwyn's son Alwyn Richard recently joined the Williams' mail-order seed supplier Medwyn's of Anglesey business after 22 years in the Welsh Guards.
Grandson Owain Richard, aged 17, recently started at Northop College. The display may also link with the 50 anniversary of the National Vegetable Society.
Williams' return coincides with the continued success of grow-your-own. He said: "It's a boom time for veg but I'm concerned people are not getting the full information they require. They are buying packets of seeds from garden centres but have no appreciation of the problems of things like carrot fly and cabbage root fly, and garden centres no longer have the products to get rid of them. Growing veg is hard work. It was never intended to be easy."
Williams said high anti-oxidant veg such as lilac and orange cauliflower were taking off and were his tips for seed sales in 2010.
Williams won 10 consecutive gold medals up to 2005 before moving on to win golds at the Hampton Court, Tatton Park, Malvern, Harrogate and Cincinatti shows in the past three years.
He said: "I just enjoy displaying veg. There is no doubt the business has grown because of exhibiting. It gives us credibility."
The pavilion display will be 6m long, 2m wide, 3m high and will include 45 types of vegetable.
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