The attack on Parsons Green was especially sinister as many children would have been on the train, but police will struggle to investigate due to cuts and poor pay.
That's according to Kevin Hurley, a former Metropolitan Police commander and counter-terrorism consultant who covered the Parsons Green area. He spoke to talkRADIO after this morning's explosion on a District Line train in London which left 18 people injured. The incident is being treated as a terrorist attack.
Hurley told Julia Hartley-Brewer: "People would have been packed on [the train] particularly children going to school which makes it all the more wicked.
"If it is following on from what we had before [in recent terror attacks] there’s every possibility it’s likely to be people following extreme salafist doctrine."
However "the police will never jump to conclusions" and although "this is what it probably is... it’s too early to say for certain."
He added: "The police are completely overwhelmed at the moment, still investigating the Manchester attacks, the Borough [Market] attacks."
But also the service has been "run down so much in previous cuts they are really struggling now to resource this and get the staff to deal with these matters.
"There’s a real crisis of investigation going on in London at the moment partly caused by the fact that many many mid-level service detectives are leaving the Metropolitan Police and going to the private sector because they’re sick of their poor pay.”
Listen to the full interview above