ISIS claims responsibility for London attack

The Islamic State has claimed responsibility for the deadly attack near London Bridge on Friday, saying via its Amaq news agency that the attacker was one of its fighters.
The suspect in the attack had served a prison sentence for a terror conviction, it has emerged.
Police said the attacker was previously convicted of terrorism offences in 2012 and had been released from prison on licence after agreeing to wear an electronic tag.
"To the best of my knowledge, the attacker was compliant with conditions imposed after his release from prison", an officer from the British counter-terrorism police said in a briefing on Saturday, adding that the police had found no evidence that anyone else was involved in the attack after carrying out searches in Staffordshire and Stoke-on-Trent.
After visiting the scene and speaking with police, Prime Minister Boris Johnson said that people convicted of terrorist offences should not be "out on early release":
"It is clear to me that this guy was out, he had served half of his sentence, he was out on automatic early release, and I have long said that this system simply isn’t working. It does not make sense for us as a society to be putting terrorists, people convicted of terrorist offences, of serious violent offences out on early release," he said.
"And we argue that people should serve the tariff, serve the term of which they are sentenced. And that’s my immediate takeaway from this," he added.
London Bridge attack: what happened?

Police say the attacker had attended an event celebrating a network bringing people together from criminal justice and higher education institutions.
It was held at Fishmongers' Hall on the north side of London Bridge.
The suspect began stabbing people inside the building before continuing on the bridge, where he was overwhelmed by members of the public, police said.
A video widely shared online shows three men — one armed with a narwhal tusk and another with a fire extinguisher — trying to pull the suspect to the ground.
Another verified video shows a man standing by the suspect — holding what looks like the tusk shortly — before police shot him dead.
George Robarts, a translator who was on the bridge at the time of the attack, said an unidentified man ran through the traffic and jumped the central partition to tackle the attacker with several other people.
"We ran away but looks like he disarmed him," he said. "Amazing bravery."
Officers had been called at 13:58 GMT on Friday and had confronted the suspect by 14:03, according to the Metropolitan Police.

Yeah. I burnt my toast the other day. ISIS claimed responsibility for that.

If organisation X publicly calls for people Y to do action Z, and they are the only ones making that call, when person Y does action Z, it is only reasonable to assume that organisation X is at least partly responsible.

i thiught isis has almost entirely been destroyed

You can defeat a caliphate's control of territory and its ability to command a structured militant force, but you can't destroy an ideology or lone wolf attacks that are inspired by that ideology.

Except that (1) Y have been doing Z for long before X have been calling for it to happen and (2) in this case, Y possibly would have done Z even without X calling for it, i.e. X's statements did not constitute a causal influence for Y to do Z and was merely coincidental to it.

We know (1) to be true and have insufficient evidence to make a factual determination on (2), but we do know that (3) X claims credit for a lot of Ys doing a lot of Zs and that this is to their benefit, which suggests that such claims should be taken with an extra pinch of salt.

'isis claims responsibility for opening of envelope'

If ISIS had been publicly calling on Muslims to open envelopes, and a Muslim subsequently opened an envelope, their claim to responsibility cannot simply be dismissed. It is only reasonable to assume that the opening of the envelope may indeed have been inspired by ISIS's encouragement.

Well, I didn't dismiss it

That is merely a reason why X might not be responsible for any given action, not that they aren't or cannot be responsible.
Therefore X's claim cannot be dismissed.