A church member told the Mirror about the moment 80 members of the choir at All Saints Church realised something serious was happening, as police snipers in balaclavas were spotted outside of the building on rooftops at around 8.20pm.
Jake Elsley, 21, said they continued singing for about ten minutes before realising they should try to "get out of the area", ensuring they kept "away from the windows".
Please pray. Were locked in the church. Shooting outside and armed police outside. This choir practice just got very scary
— Jake Elsley (@jakeelsley96) November 9, 2017
He said: "We were having a choir rehearsal and heard a helicopter overhead and could see blue flashing lights outside the church door.
"I kept seeing people in the doorway but had no idea what was going on."
Armed police closed off parts of the Portobello Road and a helicopter used searchlights to help with the operation.
After Elsley and the group were evacuated, he tweeted about not being sure what the cause of the raid was.
Some are suggesting it was an anti-terror raid. We had a helicopter overhead, police outside the church door, and road was blocked both ends with unmarked cars. Was very freaky getting asked to move and lock all doors. We are safe - thank you all for your prayers and love
— Jake Elsley (@jakeelsley96) November 9, 2017
He said: "One of the leaders tells us that there are armed police outside... that we are to lock all doors and get away from the windows.
"[It] was very freaky."
Another member of the choir told The Mirror: "We didn't really know how to respond.
"We were told to carry on singing but there was a clear level of speechlessness in the air."
A spokesman for the Met Police said: "At approximately 8pm, Trident officers conducted pre-planned operation in Colville Square.
"Five were arrested on conspiracy to commit GBH. A number of knives were seized."
The area has now been reopened.
