"I'll be totally honest with you: this has been extremely upsetting".
Fans surrounded his Land Rover Discovery and chanted "Oh, Jeremy Corbyn" to the tune of the White Stripes' Seven National Army.
Mr Corbyn has come under fire in sections of the press for declining at invitation to the official Armed Forces Day event in Liverpool because of plans to address crowds from the main stage of the Glastonbury Festival tomorrow (Saturday).
Crowds also sang the refrain as they queued to enter the festival site.
Alex wrote: "Jeremy Corbyn wearing cream pants as glasto is one of the boldest moves I've seen in years".
To big cheers, the Labour leader said he had been inspired by the surge of good will in his recent election campaign, that had defied the scorn of the right wing United Kingdom press saying: "the commentariat got it wrong".
Festival-goers took the extra checks in their stride, more concerned about coping with the hottest June for four decades which slowed activity on site to a crawl.
"The young people who got involved in politics for the first time are fed up with being, denigrated, fed up with being told they don't matter, don't participate..."
He will introduce U.S. hip hop duo Run The Jewels at the Pyramid Stage at 4pm before giving a talk at the Left Field tent.
Artists appearing at the festival have spoken of their support of Mr Corbyn's politics, while Friday night's headliners Radiohead commented during their set: "See you later, Theresa".
Mr Corbyn tweeted a picture of himself with festival staff, adding: "Just arrived at #Glastonbury".
That aside, the frontman rarely spoke during the set, except to thank Glastonbury organisers Michael and Emily Eavis "for having us at your lovely farm today". "Shut the door on the way out!"
Audience interaction was characteristically light, although there were a number of well received political references with a frenzied Yorke chanting "strong and stable" - a campaign message of Britain's much maligned Prime Minister Theresa May - at the end of "Myxomatosis". "I know how I feel about the [attack], but the fact that people spontaneously rallied around that song is an incredible thing".