Michael Mansfield, KC, head of Nexus Chambers and one of Britain’s leading barristers, said the letter should “absolutely” be considered by those investigating the incident.

“The document is plainly relevant to a particular state of mind,” said Mansfield. “In other words it is not indicating that the target of the Israeli army is primarily Hamas but Gaza as a whole by weaponising aid under siege conditions.

“Those who will inevitably suffer and run the risk of death as a result are bound to be non-combatant civilians, medics, women, children, the injured and those who are responsible for bringing aid as with the seven killed.”

Another senior British legal figure, who asked not to be named, said that while the letter may show “animus”, it was not, in their view, relevant to the question of establishing motives for last week’s drone strike.

Although the IDF has concluded its probe, a judicial inquiry is ongoing to determine whether criminal charges should be brought against those involved in the killings.

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Mandel is the highest-ranking officer to have been dismissed in connection to the airstrikes. In 2007, he was named in the Israeli media as one of the IDF’s “10 most promising religious officers”.

The son of a Holocaust survivor, he lives in Gush Etzion, a cluster of Israeli settlements in the occupied West Bank.

In his youth, he studied at a religious school run by the Ateret Cohanim, a right-wing Jewish organisation dedicated to “returning, reclaiming, and rebuilding a United Jerusalem”.

Since 2000, the organisation has been acquiring land in the Arab neighbourhoods of East Jerusalem outside the Old City.

Unanswered questions

The IDF’s internal investigation characterised the strikes, which took place at night, as a “grave mistake” and found they were “carried out in serious violation of the commands and IDF Standard Operating Procedures”.

However, it said there was no intentional harm. “Those who approved the strike were convinced that they were targeting armed Hamas operatives and not WCK employees,” said the IDF.

The investigation into Mandel and his colleagues was led by retired Major General Yoav Har-Even, president and chief executive of Rafael Advanced Defence Systems, sparking claims of bias.

The IDF is one of Rafael’s biggest buyers. The company, which sells nearly half of its arms to Israeli clients, makes the ‘Spike missiles’ which are reported to have been used to kill the aid workers.

“We demand the creation of an independent commission to investigate the killings of our WCK colleagues”, said WCK in the wake of the IDF report last week. “The IDF cannot credibly investigate its own failure in Gaza”.

The IDF investigation report, which runs to 539 words, identified three key errors it said led to the strike:

• a failure by the forces involved to identify the vehicles as belonging to WCK as they left the WCK warehouse for the evening
• the mistaken assertion that an armed man had entered one of those vehicles
• the destruction of the second two vehicles after the first one was hit

On the eve of its publication, a briefing was given to a small group of foreign journalists by Har-Even, but key questions were left unanswered.

Chief among them is how it was possible the drone team did not know the vehicles belonged to WCK and why it was thought a gunman had got into one of the cars.

“I think it’s inconceivable that the IDF wasn’t aware that the three vehicles were being driven by the WCK aid workers,” said Charlie Herbert, a former major general in the British Army who served in Afghanistan and Iraq.

“I cannot comprehend how they could have mistaken them for anything else, and if there was uncertainty, the strike shouldn’t have gone ahead.”

The alleged failure to realise the cars belonged to WCK is perplexing for a number of reasons but mainly because the entire WCK operation had been approved in advance by the IDF and had been tracked for hours, almost certainly days, by the IDF and its drones.

The IDF said the vehicle’s roof markings were not visible to its drones at night. But the drones had tracked the WCK aid convoy from the beach, where the supplies had been landed on a pier built a few weeks before under the glare of world media attention.

The trucks were then tracked all the way to WCKs warehouse in Deir al-Balah, according to the IDF. The same journey had been made the previous day and several times before. Each journey was approved by and closely monitored by the IDF.

“The IDF has acknowledged that our teams followed all proper communications procedures”, said WCK in a statement. “The IDF’s own video fails to show any cause to fire on our personnel convoy, which carried no weapons and posed no threat”.

On the day of the strikes, it was Mandel’s Nahal Infantry Brigade that was embedded on the ground in the area and was tracking the convoy. IDF protocol demands that one or more of its officers would have been in live radio contact with the teams flying the drones above.

The drones are believed to have been controlled from Palmachim Air Base, which is just south of Tel Aviv and 70 kilometres to the north. Squadron 161, known as “The Black Snake” unit, operates the Elbit Systems Hermes-450 “Zik” drone from Palmachim where it specialises in counter-terror missions over Gaza, the West Bank and Lebanon.

The drones can carry up to four Spike anti-tank guided missiles of the sort made by Rafael Advanced Defence Systems.

It is known with certainty the IDF knew the convoy belonged to WCK as it moved from the beach to the WCK warehouse. This is because Har-Even told journalists that the military had called WCK’s US office to tell them a gunman had clambered onto one of the trucks at the time.

As Eylon Levy, until recently an Israeli government spokesman, has said on social media, it is “normal” for armed gunmen to clamber onto the top of aid trucks in Gaza.

While the aid was unloaded at the warehouse, the two drones kept circling, according to the IDF. Once the aid was stowed, four SUV vehicles were observed by the drone emerging from the WCK warehouse.

One vehicle headed north and the drones watched as the aid workers got into the three remaining WCK vehicles to return home for the night.

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At this point, said Har-Even in his briefing, someone watching the video feed from one of the drones said they thought one of the people getting into one of the vehicles was carrying a weapon.

However, when the video was rerun for the investigators there was no sign of that. “No footage of this moment was provided”, reported the BBC from the briefing. “But the military investigation concluded that it was a ‘misclassification... they saw that it’s a rifle but at the end of the day it was a bag’.”

Former Army commander Colonel Hamish de Bretton-Gordon said the drone team would have found it difficult to discern what was happening on the ground at night but added that the strike should not have gone ahead if “there was any doubt” among the IDF officials.

“In the British Army, we were not allowed to approve an airstrike based on an assumption,” he said.

It was on the basis of this single alleged “misidentification” that the IDF investigation says the three vehicles containing the seven aid workers were hit.

Without this alleged misidentification it would also be difficult for the investigation to justify its conclusion that “those who approved the strike were convinced that they were targeting armed Hamas operatives and not WCK employees”.

The two officers removed from their positions - Mandel and the brigade fire support commander, an officer with the rank of major who has not been named – were dismissed for acting in “serious violation” of IDF Standard Operating Procedures.

Specifically, the investigation found the strikes breached these procedures in two ways:

The suspicion an armed man was in the first car was insufficient to justify the strike
The second and third vehicles were destroyed without any further evidence being gathered

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An IDF spokesperson told the Telegraph, London: “As concluded in the investigation, a chain of serious failures led to a situation where the forces that struck the convoy were not aware of the fact that the vehicles belonged to the WCK organisation at the time of the strike, and believed that they were Hamas operatives.

“Following the operational failures that emerged in the investigation, the chief of staff decided to dismiss the relevant officers. In addition, the findings of the investigation were forwarded to the Military Advocate General’s Corps for the purpose of making a decision regarding the opening of a criminal investigation by the military police.”

Mandel was also approached for comment by the Telegraph, London both via telephone and the IDF.