London, Japan, Cassini: Your Friday Evening Briefing

Here’s what you need to know at the end of the day.

(Want to get this briefing by email? Here’s the sign-up.)Good evening. Here’s the latest.1. The Islamic State claimed responsibility for the crude bomb that exploded on a crowded train in London this morning, leaving 29 injured. It was the fifth terrorist attack on Britain this year.There has been longstanding concern that militants would target the London Underground, known as the Tube, as they did in 2005. The government raised the national threat level one notch to “critical,” the highest....