The renowned philosopher was shouted down by more than a dozen protesters during the debate about cuts to the arts at Foyles bookshop in central London.
At the end of the heated hour-long debate, during which Prof Grayling was verbally abused by students protesting against his plans, protesters set off a smoke bomb.
Prof Grayling and the three other speakers were quickly ushered from the room as it filled with pungent red smoke. Organisers were forced to evacuate about 100 people amid fears for the safety of the crowd just moments after Prof Grayling said he would talk to the protesters.
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