Footage posted on social media appears to show a man repeatedly trying to pull a wooden cross from its base above the entrance to Chadwell Heath Baptist Church in Romford.
With the hood of a coat placed over the cross the man can be seen using all his force to release the cross from the roof of the church.
Today workmen were preparing to put the cross back on the roof.
A local cafe owner who witnessed the desecration said: 'I saw the guy first when I was opening up at 8am.
'He was sitting on the pavement bobbing his head back and forth.
'You could tell he had mental health issues. I don't think he was local because I'd never seen him before. I think he might have be Algerian or Moroccan.
'He disappeared for a while after I first saw him, but then the next thing I know he's climbed onto the church and he's shouting random abuse.
'He was very angry and he started damaging the cross.
'He was shouting about religion but to be honest he wasn't making much sense.