"What do you do young man?" asked Margaret Thatcher with her characteristic English bark. It was 1982, and the then British prime minister was on a visit to CERN, the European laboratory for particle physics where scientists were looking to understand the most minute workings of the universe.
"I think of things that the experiments can look for, and I hope that the experiments find something different," replied a young John Ellis.
"Wouldn't it be better, young man, if they found what you predicted?" she said.
Ellis replied: "If all that they found was exactly what we'd predicted we wouldn't have any clues as to how to advance. What we really want is something that is at least a bit different."
Cut to the modern day: John Ellis, now 66, is one of the foremost experts in the field of particle physics. Ellis has appeared on and in the pages of and , as CERN, its Large Hadron Collider and the elusive Higgs particle they may have helped discover became the stuff of sexy science.
"CERN scientist shows The Post the lighter side of Higgs boson", Video by Hedy Bok and Silvio Carrillo
"At CERN we don't make enough antimatter to power the Starship Enterprise or blow up the Vatican," he tells a packed auditorium at Hong Kong University of Science and Technology, with reference to CERN's role in Dan Brown's novel turned film .
Ellis was in town to talk about the Higgs boson and the fundamental questions of the universe that physicists are trying to address today: Where do we come from? What are we? And where are we going?
He looks like a cross between Father Christmas and Gandalf. But on stage the bushy white beard, shoulder length hair and intense, maybe even slightly intimidating stare gives way to a soft English lisp that gives the Commander of the British Empire an approachability that he might not have otherwise.
"It's important to share what we know with the public," he says. "The public has a stake in what we do, not just because they pay for us, but because what we do will affect them."
He punctuates his speech with jokes, keeping his audience entertained throughout a lecture that could have been as dry as dust. Puns, silly photographs, and even a mock striptease to show off a T-shirt with Maxwell's equations and the Standard Model predicted by Higgs and others, proudly emblazoned on the chest.
He throws out facts to help make the importance of physics seem less abstract. Some 37 per cent of United States' gross domestic product depends on discoveries, he says. The internet was created by physicists who wanted to share their data with collaborators from across the world.
The Large Hadron Collider is only one of 30,000 or so particle accelerators in the world, he notes, most of which are being used in medical facilities the world over.
"You know the 'P' in Positron Emission Tomography [PET] scans?" he asks, referring to technology that can help monitor neurological problems, heart disease and cancer. "The Ps, the positrons, are created by particle accelerators."
But in a field where you may go an entire career without seeing the fruits of your labour, it's not all of these practical applications that have kept Ellis questioning and communicating. It's that fundamental question about existence: what are we?
Such questions can elicit the most airy of answers. Conversely, though, one of the most abstract of professions - theoretical and particle physics - is based on some of the most grounded of facts.
Ellis explains that the same small particles, such as electrons, neutrons, quarks, quasars and the like, make up everything in the galaxy, the stars, you, the oceans.
"Sometimes we physicists forget to be amazed that most of what we see in the universe is made up of the same constituents," he says.
But even though physicists have been able to prove the existence of atoms and the like, there are still parts missing from the picture.
There are theories about other particles yet to be discovered - including, until recently, the Higgs boson, whose existence was confirmed at CERN last year.
These particles, how they interact, how they interacted in the past and will do in the future could provides answers to crucial questions about where we come from and where we are going.
Particle physics has been part of what helped make the "big bang" theory the best model for our origins and where our universe is headed. The work on the Higgs boson, in which Ellis has played a key role, provides more possible paths to understanding how our universe works.
It is towards the end of Ellis' talk that he comes to the part about meeting the prime minister and his defence of his science.
"Mrs Thatcher didn't understand because Mrs Thatcher liked to find things to be the way she wanted them to be."
For Ellis, like other physicists, it's not just about having the right answers. It's about finding out there's more to life.
Clerk Maxwell Professor of Theoretical Physics, King's College London
CERN, King's College, London.
Commander of the British Empire (2012), Maxwell medal and prize (1982), Paul Dirac medal and prize (2005)
Pioneering research on the connection between particle physics and cosmology; the Higgs Boson; and ideas about supersymmetry - upon which rests string theory, a favoured candidate for a theory of everything. Ellis is also one of the most cited physicists in the world - with more than 50,000 so far. He has also been instrumental in bringing scientists from across the world - from Cambodia, Mongolia, for instance, to do research at CERN