Parliamentary authorities said someone got out of the queue on Friday and tried to approach the coffin on its platform. The Metropolitan Police force said a man was detained for a suspected public-order offence.
A statement from Scotland Yard said: "Around 22.00hrs on Friday 16 September officers from the Met's Parliamentary and Diplomatic Protection Command detained a man in Westminster Hall following a disturbance.
"He was arrested for an offence under the Public Order Act and is currently in custody."
It comes after a 19-year-old man allegedly exposed himself and pushed into mourners from behind as they waited in the line at Victoria Tower Gardens on Wednesday.
Adio Adeshine is said to have gone into the River Thames in an attempt to evade police before coming out and being arrested.
He was remanded in custody on Friday after appearing at Westminster Magistrates' Court charged with two counts of sexual assault and two counts of breaching a sexual harm prevention order.
The tide of people wanting to say goodbye to the Queen has grown steadily since the public was first admitted to the hall on Wednesday. On Friday, authorities temporary halted letting more visitors join the end of the line, which snakes around Southwark Park some eight kilometres from parliament.
Overnight, volunteers distributed blankets and cups of tea to people in line as the temperature fell to 6C.
Members of the public kept silently streaming into Westminster Hall even as the ueen's four children — King Charles III, Princess Anne, Prince Andrew and Prince Edward — stood vigil around the flag-draped coffin for 15 minutes on Friday evening.
All eight of the Queen's grandchildren are due to stand vigil beside her coffin on Saturday.
The lying-in-state will continue until Monday morning, when the Queen's coffin will be borne to nearby Westminster Abbey for her state funeral.
with PA
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