Mr Chessum, a high-profile student activist, was arrested today following a demonstration yesterday against the closure plans, where there was a heavy police presence.
ULU said in a statement that the arrest was “a clear attack on the right to protest”.
A Metropolitan Police spokesman said a 24-year-old man had been arrested under Section 11 of the Public Order Act, which covers the requirement for “advance notice of public processions”.
He is being held at a central London police station, the spokesman said tonight. Dozens of students and staff from the university have been gathering outside the station - believed to be Holborn - to demonstrate against his arrest.
In May, the University of London’s collegiate council decided that ULU – Europe’s largest student union – should be wound up and its Bloomsbury headquarters put in the university’s hands.
That decision has sparked fierce opposition from ULU, led by Mr Chessum.
The Met’s spokesman said that police officers at yesterday’s demonstration at ULU had “attempted to engage with event organisers, who had said there was no procession route planned”.
But there was then a “procession down towards Senate House [the administrative centre of the University of London], where there was a clear intention by those present to breach security at Senate House and enter the premises and disrupt normal activity at the venue”, the spokesman said.
Officers “acted to support the security of the venue” and protesters were “not permitted to enter”, he added.
ULU’s statement said Mr Chessum “was intercepted by several police officers outside the ULU building on Malet Street in Bloomsbury, on his way back from a meeting with University of London management”.
It added: “The arrest follows a similar incident in July, during which an activist was arrested for allegedly chalking slogans in support of a campaign for sick pay, holiday pay and pensions for University of London workers.”
ULU called the arrest “a transparent and shameful attempt to intimidate students from demonstrating against the actions of university management”.