The leader of the far-right BNP, Nick Griffin, and the controversial historian, David Irving, have arrived at the Oxford Union for a debate.
Police have said they will manage the event like any other
They have been invited to the free speech event by university students but anti-racism campaigners say they should not be given a platform to speak.
The men arrived at about 1600 GMT, four hours ahead of the debate's start.
Protests are expected as their inclusion has led to objections from student bodies and opposition groups.
MP Dr Julian Lewis has also resigned his membership of the Oxford debating union in protest.
The Oxford Union says it is important to give people of all views a platform.
A rally against the inclusion of the two men was held last week with speakers including Holocaust survivors.
The decision to give Mr Griffin and Mr Irving a platform has also been condemned by the president of the Oxford Student Union and race equalities watchdog Trevor Phillips.
Mr Griffin has repeatedly insisted the BNP is not a racist group.
He was convicted in 1998 for incitement to racial hatred for material denying the Holocaust.
Mr Irving was imprisoned for three years after pleading guilty to Holocaust denial in Austria.
But the debating union voted by a margin of two to one to allow the two men to take part in the debate.
In his resignation letter Dr Lewis, shadow defence minister and MP for New Forest East, described the two men as "a couple of scoundrels".
Nick Griffin and David Irving are due to speak at the Oxford Union
He told the BBC: "I think it is a very small way of making a personal protest against a very foolish and counter-productive decision - a thoughtless and self-indulgent decision - by the Oxford Union.
"I think there are people who are confusing this with an issue of free speech. It's not an issue of free speech to offer someone a privileged platform from a prestige organisation."
But Oxford graduate and novelist Diran Adebayo said: "We're in a culture in this country, with the smoking ban etcetera over the last 10 years, where people seem to be very keen to ban pretty much anything that they can.
"This seems to me to be relatively reasonable to invite these two people. Nick Griffin is a leader of a political party, David Irving is an academic and historian, let's hear what they've got to say."
Mr Griffin and Mr Irving's invitation has seen high-profile speakers withdraw from the platform including Defence Secretary Des Browne.
It has also been opposed by the university's Muslim and Jewish societies along with anti-fascism leaders, who are organising Monday's protest.
But Liberal Democrat MP Evan Harris, who is billed to speak at the forum, said it was the "views of these extremists which are a disgrace" and "not their right to hold their views".
He added: "The measure of our country's respect for free expression is our willingness to allow it for the most objectionable and offensive lawful speech, not just for those with whom we agree."
Simon Darby, BNP spokesman, described the expected protests as "very misguided".
"It is ironic you have got people shouting 'fascism' while campaigning in the face of the process of democracy," he said.
A Thames Valley Police spokeswoman said the expected demonstration would be policed "like any other protest".