How do we know 'White Widow' has been killed

Establishing the success or failure of a drone strike in Syria is hard. 

Ideally special forces would be sent to the scene to gather DNA and other evidence for proof, but in Syria that is rarely practical or possible.

Instead, analysts examine cockpit footage from either the drone or jet which carried out the strike. This is known as battle damage assessment - or BDA for short.

Conclusions are made using the best available information but this cannot always be 100% certain, hence the caution from officials if this information ever comes out into the public domain.

Ideally, the video feed will be conclusive; separately agents working on the ground might be able to corroborate a successful strike.

Web traffic is monitored for confirmation among other jihadists.

British defence officials are confident in this case that Sally Jones was killed, but have questioned some of the more precise detail being reported by the media - the where and when.

Essentially though, they've got their woman, the latest high-profile scalp in what is now a sizeable operation to remove Islamic State's key figures.

An extensive and high-level drone operation has been established in the Middle East by the British and Americans.

The aircraft themselves fly out of an undisclosed base in the region but are piloted remotely from cockpits in Lincolnshire and Nevada.

The control centre is in Qatar - it is here that all the live feeds from aircraft are fed into an operational hub.

It's also from here that senior officers order strikes using all the evidence and legal advice available to them.

Intelligence on targets is gathered through human sources and communications data. Drones can then fly above a target for hours or even days, monitoring patterns of life and waiting for the precise moment to strike.

The decision to strike can be taken within seconds or after hours of consideration. In rare cases, the Defence Secretary will have pre-authorised the killing of certain high-profile individuals.

Jones was reportedly killed trying to leave Raqqa. This would tally with recent intelligence from the city.

"Key commanders will spread themselves around a place," a British military intelligence officer told Sky News last month.

"We saw the movement out of Raqqa from these types of people much before the Raqqa operation really started in earnest."