Warm and dry weather meant more than 20,000 attended, 15 per cent up from the expected 17,000, though many exhibitors struggled to find plants in flower after the coldest winter in 31 years.
Local cyclists and the Green Party protested against heavy show traffic. The RHS agreed to a 30-minute roadblock on an access road as long as the protesters left afterwards.
RHS shows organiser Stephen Bennett said: "When there is a public protest, within reason we let it happen - we have at Chelsea Flower Show with gnomes. If people want to protest, let them. There was no public hazard involved, so why inhibit people's free expression?"
Exhibitor Derek Jarman of Hayloft Plants said: "It was good for the Green Party's election campaign but not good for exhibitors. The RHS handled it very well though."
Bennett added that the Icelandic volcano meant BBC weather forecasts to be broadcast from the site were shelved - but that did not stop a record-breaking start to the show season. He also revealed that the new RHS director-general might be announced as soon as the Chelsea Flower Show.