Perhaps the most difficult job at Chelsea falls to the judges. Sally Nex talked to show organiser Bob Sweet about the standards set this year.

Bob Sweet is the man responsible for organising the judging, which takes place in two stages – an assessment, on Sunday, followed by formal judging on Monday. He says the discussions during which medals are decided are long and sometimes fierce. “There’s always quite a strong debate about which one should take the lead, and I think perhaps there is always the feeling that it ought to be a garden which offers something slightly alternative,” he says.

He believes the standard at this year’s show is particularly high, though he describes Tom Stuart Smith's Daily Telegraph garden as an “obvious pick” for best in show. “He's gone for a garden which offers a lot of new material, it has this Corten [pre-rusted] steel in it, and it has a very bold range of plants in it. And it has this huge viburnum, which is quite a difficult plant for designers to use.”

There haven’t been many golds in the small gardens category this year – just one awarded for the City Gardens, and two in each of the Chic and Courtyard categories. “That’s pretty typical,” says Bob. “The small gardens category has got a very high number of first-timers, and therefore it’s not surprising that some of those don’t quite make it to the top of the tree.”

In the Great Pavilion, almost half the exhibitors were awarded gold medals in a particularly high-quality year. One of them was the Kirstenbosch exhibit from South Africa, a stand which particularly caught the judges’ eye. “They’ve taken lack of water for their theme, so they’ve produced a display which has a big water feature in it, but only uses five litres of water,” says Bob Sweet. “It’s a stunning display – it just shows you, even with a little water how much of an impression you can make.”

As for trends at this year’s Chelsea, Bob says the new star of the design world is Corten steel – otherwise known as rusty metal. “It’s been hobbling around on the side for a while, but in several areas of the show we’ve suddenly seen rusty metal appearing now. That feel of having that lovely brown colour, that rusty-type structure - there’s no doubt that that’s going to have a big future.”