Roger Hallam is now on his eleventh day without food, and won't stop until the London university stops investing in coal, oil and gas companies – which he claims could happen within a week.
Mr Hallam told The Independent: "Someone somewhere has to make a stand. We're absolutely, objectively, scientifically in a climate emergency, and anyone with any doubt around that is scientifically illiterate.
"But everyone's drunk on fossil fuel. We're in a completely warlike situation."
He described the sensation of starvation: "You feel like you've got a mild virus. I've gradually got weaker, I haven't had any physical energy, but I'm perfectly mentally fine.
"I was getting really paranoid yesterday. The bile goes into your stomach and makes you sick, it's the most dreadful feeling.
"After 14 days the fat on your body starts disappearing. At some point after that, its game over. But I don't think I'm going to drop dead – I am a skinny vegan, after all."
According to a 2013 Freedom of Information Request, KCL has more than £8 million invested in fossil fuels but no investment in renewable energy. Their reluctance to divest has inspired years of protest.
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Mr Hallam and another student member of the King’s Climate Change Emergency (KCCE) campaign group were arrested last month after spray-painting slogans in KCL's main hall.
He was charged with criminal damage and fined £500, but has since been allowed back onto the central London campus. Around 20 other activists have carried out 24-hour hunger strikes in solidarity with Mr Hallam.
Though these actions were the work of a small group of campaigners, 96 per cent of a sample of 160 KCL students backed calls for full divestment in a recent survey conducted by KCCE.
Anti-apartheid activist Archbishop Desmond Tutu, who studied at KCL for several years, is a staunch supporter of divestment who has called for the university to withdraw from all fossil-fuel funds.
But Chris Mottershead, the vice principal in charge of KCL staff and students, spent 30 years working for oil giant BP.
Though he believes there is a measure of "corporate support which leads to corruption of ethical priorities and legal priorities", Mr Hallam lays the blame for KCL's sluggish response to years of climate campaigning on "organisational inertia".
The 50-year-old PHD researcher met with Mr Mottershead last week, and said the VP offered a package including full divestment by 2020, bringing green investments up to 50 per cent by 2025, and increased research funding for climate change activists.
If it materialises, the new pledge will mark a significant step up from the university's previous commitment. That offer focused only on the "dirtiest" fuels like tar sands oil or thermal coal, and offered no solid commitment beyond a vague 2029 deadline on "becoming a sustainable institution."
A KCL spokesperson said: "We recognise the rights of our students to campaign for change and we always welcome open and responsible dialogue on such matters of global importance and concern.
"As a responsible university, we take climate change very seriously and are committed to playing our part in the vital transition to a low carbon economy. We have chosen to follow actions that deliver real and measurable benefits.
"The university continues to work closely with the student-led Fossil Free King’s organisation to develop a socially responsible investment plan and we published our position in September last year. "
But Mr Hallam believes he'll be eating within the week. He said: "Once we've got a solid statement [confirming the new pledge], I'm going to come off the hunger strike. We basically transformed the political ground in 8 weeks.
"To my knowledge, there have been no other arrests over divestment at universities.This is a groundbreaking campaign for how to combat this system, a model that can be replicated.
"This ethical, moral, polite but consistently transgressive action hasn't damaged any students – and it's won."