By Gemma Strong One of the King’s senior gardeners, who has worked at the monarch’s Highgrove House for 20 years, has revealed the simple four-step method that’ll banish common garden pests. Green-fingered folk will know what a nuisance slugs and snails can be, taking over outdoors spaces and destroying plants along the way. Luckily help is at hand, courtesy of Jack Stooks, who has spent the last two decades tending to the King’s Tetbury estate. And he has shared his wisdom when it comes to dealing with these slimy menaces – with a four-step method. First up, Jack advises putting fermented yea…