Detectives have made "immense" progress in the investigation into the Manchester bombing and are confident they have arrested some "key players", Britain's top counter-terror officer has said.
Assistant Commissioner Mark Rowley said police have made "significant" arrests and "finds" and have got hold of a "large part of the network" being sought over the atrocity.
Mr Rowley said: "They are very significant, these arrests.
"We are very happy we've got our hands around some of the key players that we are concerned about but there's still a little bit more to do."
Mr Rowley disclosed that police have reviewed security at more than 1,300 events around the country ahead of the bank holiday weekend.
Britain remains at the highest threat level of critical, meaning an attack could be imminent.
The senior officer issued a message of reassurance to the public.
"Go out as you planned. Enjoy yourselves and be reassured by the greater policing presence you will see.
"We can't let the terrorists win by dissuading us from going about our normal business."
Twenty-two people were killed when Salman Abedi launched a suicide attack at an Ariana Grande concert at Manchester Arena on Monday night.
It was the worst terrorist atrocity to hit Britain since the July 7 attacks in London in 2005 and sparked a huge counter-terror probe.
Since Tuesday a total of 10 people have been arrested, with eight remaining in custody.
Two were released without charge.
Providing an update on the probe, Mr Rowley said it was likely further arrests would follow.
He said: "Having made enormous progress and made some significant arrests and had some significant finds, there still remain important lines of inquiry for us to pursue.
"We've got to try to understand everything we can about the dead terrorist, his associates.
"We need to understand the whole network and how they acquired and built the bomb that exploded on Monday night.
"It's going to take a little more time to close down those gaps in our understanding.
"We are working as fast as we can do because everyone wants answers to this."
He said police now have a "much better understanding" of what happened.
Mr Rowley went on: "We've got a lot of the risk contained but we still have some uncertainty.
"As we chase down those lines of inquiry we will keep this strong policing presence.
"We need to grow our confidence that we have got every component of the network and we have got as full an understanding as possible about how the device was constructed and whether there's any remaining risk.
"Clearly we haven't covered all the territory we want to but we have covered a large part of it.
"Our confidence has been increasing over recent days but there's still more to do to get to the degree of confidence we want."