Captain David Hicks, of 1st Battalion The Royal Anglian Regiment, died from shrapnel wounds during a Taliban rocket attack on his base north east of Sangin, in Helmand Province, in August last year.

Despite suffering mortal injuries in the attack, the hero officer ripped off his oxygen mask and shouted "Let me get back out there" as medics tried to treat his open chest wound.

He was posthumously awarded the Military Cross for his bravery.

Yesterday, the day after a memorial plaque was unveiled at the private school where the 26-year-old was educated, an inquest heard conditions at the base offered "limited protection" to soldiers when Capt Hicks was killed.

Protective walls were too low, there was no doctor on site and some soldiers slept under makeshift netting, the hearing was told.

Recording a verdict of unlawful killing, Wiltshire coroner David Masters said: "I don't think making do is an acceptable proposition for our forces in Iraq and Afghanistan. I'm very anxious about that."

The inquest heard that Capt Hicks, who had served with the Royal Anglian Regiment since 2002 and lived in Wokingham, Berkshire, was killed during an attack just after 1pm on August 11, 2007.

The Inkerman base, where he was stationed, had originally been opened as an Afghan national army base in May 2007, but was expanded to include 80 British troops in July that year.

Capt Hicks was scouting the location of Taliban troops at the top of a 'sangar' observation post when his position was struck by an anti-tank missile, injuring Capt Hicks and several other soldiers.

Capt Hicks was carried from the sangar by his men and shouted "get me back there" as he drifted in and out of consciousness, the inquest heard.

He was transported by Chinook helicopter to a medical facility at Camp Bastion, but did not survive.

The coroner said the makeshift conditions at the base had not provided enough protection against such attacks.

"They had netting over the walls and that was their accommodation. That gave no protection," he said.

The coroner also criticised medical facilities at the base after hearing that Capt Hicks had had to be treated on the floor because the medical room was full to its capacity of one.

He said: "He couldn't be treated in the room – there was an Afghan National Army soldier in it. He was then treated by a medic – not a doctor - a medic."

Pupils and staff gathered at Oundle School on Sunday for a Remembrance Sunday service, including the dedication of a plaque in memory of Capt Hicks.

Capt Hicks has been described by his superiors as an "outstanding officer" who provided an "inspiring example to his men".