Hundreds of thousands of children have been scraping, grating and wrapping vegetables as part of the largest ever live cooking lesson led by Jamie Oliver and streamed by TES today. 

The day began in Australia, where thousands of children cooked Jamie’s Rainbow Salad wrap, during a 30-minute lesson at Sydney Showground.

Then at 2pm BST, Oliver hosted a live lesson from City Hall in London - a building the present mayor, Boris Johnson, has nicknamed ‘the onion’.

“We’ve already broken the world record with just under 3,000 kids in Australia,” Oliver told the invited audience, which included 30 lucky children from five different schools.

Each were prepped with aprons, graters and bowls - ready to make the rainbow wraps along with the TV chef. “But that ain’t enough for Food Revolution Day 2014,” Oliver continued. “We want to have the biggest cooking lesson in the world over 24 hours.”

Globally nearly 10,000 schools registered with TES to take part in the lesson learning how to make rainbow wraps - a tortilla sandwich stuffed with cabbage, pear, carrots, beetroot and feta cheese covered in a minty-yoghurt dressing.

Former Radio 1 DJ Chris Moyles was also at the event, providing updates on what was happening around the world. Schools as far afield as the US, Bosnia, Estonia, Greenland, South Africa and Spain got shout outs and a there was a special mention for German celebrity chef Tim Maelzer, who is campaigning for food education in German schools.

“Everyone thinks their country is so different,” said Oliver. “But the need for food education in schools is global.”

At City Hall grating up carrots and shaking up dressing were pupils from Altofts Junior School in Wakefield, Ysgol Carno in Powys, Isle of Portland Aldridge Academy in Dorset, St Andrew’s secondary in Leatherhead, Surrey, and Copmanthorpe primary, Yorks.

Matthew, 10, from Copmanthorpe, said: “It was great to see Jamie Oliver live and the wrap was lovely.”

Tim Williams, deputy head of Copmanthorpe, said: “So many kids wanted to do it that I asked them to write application letters. We brought six really enthusiastic Year 5 pupils and the rest of the school - 384 pupils - are watching it on a screen in the hall.”

Ffion, 11, of Ysgol Carno, said: “I like cabbage. I am not a fan of beetroot, but I tried a yellow one and it was really nice. I think I’ll make the wrap at home. I think I’ll make it for my packed lunch.”

After the event London mayor Boris Johnson popped in to greet Oliver. Speaking to TES afterwards, Johnson said: “Healthy school lunches are incredibly important. We’ve been working with the boroughs and the government to push it forward. I think Jamie Oliver is doing a great job.”

Then, asked about school meals for all, he joked: “I’d stop all packed lunches and feed them healthy liver and cabbage. It would have them quivering with energy.”

Oliver was leading the attempt for the Guinness World Record for most participants in a cookery lesson in 24 hours across multiple venues.

It was the highlight of the global initiative Food Revolution Day. Jamie’s Food Revolution network was set up by Oliver after winning the TED prize in 2010. It links voluntary ambassadors in more than 85 countries who work to make healthy food accessible to all.

In an interview with TES last month Oliver said he was optimistic that the time was ripe for the changes needed to combat childhood obesity.