Six people were arrested on Sunday after they were suspected of planning to disrupt the London Stock Exchange from opening this week.
The plot was linked to a Palestine Action group that was allegedly planning to stop the LSE opening for trading on 15 January.
The activists planned to block two front entrances by attaching themselves to the building.
Of the six arrested, a 31-year-old man was held in Liverpool on suspicion of conspiracy to cause criminal damage, alongside a further five people who were detained in Liverpool, London and Brighton.
The attack was said to have “serious implications” had it been carried out successfully.
Sian Thomas, detective superintendent of the Met, said: “Mindful of the suggestion that this was one part of a planned week of action, we are in contact with the City of London Police as well as other forces across the UK to ensure that appropriate resources are in place to deal with any disruption in the coming days.”
The attack follows two similar politically motivated events in April, when Euronext’s Paris offices were stormed by protesters angry with President Emmanuel Macron’s pension reforms.
Shortly before, protesters also infiltrated the offices of BlackRock in Paris.