Iran launched unsuccessful attack on UK's Diego Garcia

https://www.bbc.com/news/articles/c5yljdgwppzo

Foreign secretary denounces 'reckless Iran threats' after missiles fired at Diego Garcia

Iran reportedly fired two ballistic missiles at Indian Ocean base, but neither reached the target.

Iran repeatedly stated that they will not attack any country's assets if they do not assist the US/Israel. Most European countries have refused to take part, the UK decided to help so this seems like a very easy situation to have avoided.

From TFA:

> It is understood the attempted air strike occurred before the UK agreed to let the US use British military bases to hit Iranian sites targeting shipping through the Strait of Hormuz.

US moves B-2 stealth bombers to Indian Ocean island in massive show of force to Houthis, Iran

The Pentagon has sent at least six B-2 bombers – 30% of the US Air Force’s stealth bomber fleet – to the Indian Ocean island of Diego Garcia, in what analysts have called a message to Iran as tensions once again flare in the Middle East.

CNN
I don't think the article you linked disagrees with what I've quoted from the BBC, does it? Aircraft being present at the airbase isn't the same as aircraft launching for an attack from the airbase.
True on technicalities. If it isn't useful to the operation of the bombers in the region, why did it happen? And if it is useful that sounds like a UK base participating in the war

I'm no war strategist but I'd guess they did it to have them ready to strike Iran if needed. Diego Garcia has been used by UK/US joint operations in the Middle East since the Iraq War, it's not unusual to have American bombers stationed there when the US is on "high alert" or whatever.

To be clear, I'm not saying I support any of this Iran nonsense from Trump. I am very much against him meddling in the ME.