The London Ambulance Service has tweeted that members of its hazardous area response team remain on standby at The Shard. They were reportedly called to the protest at 4.40am this morning.
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The man was taken early this morning to a south London police station where he remains in custody.
The Chancellor faces tough talks to build a Government while also dealing with the challenge from a resurgent far right.
Watch John McDonnell's speech at Labour Party conference 2017 live as he speaks to Brighton the audience from 12.15pm.