Usually if a concern is raised, they'll check the file and see if the concerns received meet the threshold. Then they will hold a strategy meeting, inviting all professionals known to a family/child, sometimes, depending on the nature of the concerns, police will also be present. If the concerns raised within a strategy meeting meet a set threshold, a S.47 investigation is initiated. These are either single or joint agency.
Sometimes when concerns are of immediate risk there is what's called a police protection order (PPO).
Strat meetings and then visits can be held the same day as a concern is received if deemed to be serious enough