Parsons Green Terror Attack - 2 suspects questione

The transcript details a police investigation into a bombing incident on a train at Parsons Green Station. Two suspects, aged 18 and 21, were arrested in connection with the incident. The investigation involved searches of properties linked to the suspects, including a home in Sunbury. The national threat level was reduced from critical as progress was made in the investigation. The operation is ongoing, with armed patrols expected to return to normal levels soon.

What was the national threat level status after the arrests?

What does the investigation indicate about the progress made?