The anti-war protestors assembled at the west entrance to the complex as the event opened. The crowd then moved to a bridge outside the venue at around 1.20pm, before moving along to the Victoria Dock area.
A Metropolitan Police spokesperson told Event that no arrests had been made and the protest had been "peaceful".
It is not clear whether there is one group behind the protest, but an organisation known as CAAT (Campaign Against Arms Trade) has been calling for people to join the march.
A statement on its website reads: "Join CAAT to demonstrate that helping private companies profit from conflict and insecurity, and organising events – where human rights abusers, warring states and countries with desperate development needs can increase their armaments – is not a 'legitimate' use of public resources."
Clarion Events, which organises the event, and Excel were unavailable for comment.
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