Complex sentence: By 4.30pm (BST) police estimated there were 500 chanting protesters, and some 25 people who had penetrated the main entrance of Television Centre after breaking through a cordon were expelled.
Split into simpler sentences: By 4.30pm (BST) police estimated there were 500 chanting protesters. Around 25 people who reached the main entrance of Television Centre after breaking through a cordon were expelled.