Descendants of a Second World War airman killed with his colleagues on their first mission are being sought by another crewmen’s relative to attend a one-off commemoration next year.

Flight Officer John Joseph Knowles, of Willesden, was only 23 but the joint oldest aboard when he perished along with six others in their Lancaster bomber during their debut raid to Stuttgart.

The aircraft was shot down by a night fighter on March 15 1944 and crashed near the village of Bolstern in south-central Germany.

Louise Dexter, of Hook, Hampshire, the niece of one of the seven crewman, said: “I have been researching the aircraft and her crew for over two years and as a result, I have found the relatives of four other crew members - the Pilot, the Navigator, the Rear Gunner, the Wireless Operator/Air Gunner and my uncle, who was the Flight Engineer.

“Together we have also found the site of the crashed aircraft and eyewitnesses from the local German village.

“Next year, on the 70th anniversary - 15th March 2014 - the families of the relatives and the local people from the village of Bolstern will unveil a memorial to the crew.

“In 1944, after ND474 had crashed in a field next to the village, the local people removed the seven dead airmen and buried them in their village churchyard, where for several years the villagers tended to their graves until the bodies were finally laid to rest in Durnbach War Cemetery (near Munich).”

Mrs Baxter wants to trace members of Flight Officer Knowles’ family so they can be present at the special ceremony next year.

Villagers in Bolstern have allowed the crewmen’s relatives a spot besides the field where the aircraft crashed to install a memorial stone onto which two inscribed brass plaques in English and German will be mounted.

“Seventy years to the day, the families of the crew will be unveiling a memorial to the brave men of ND474,” she said.

“We will ensure that the sacrifice they made for our country will never be forgotten.

“It is therefore really important that we find as many relatives of the crew as possible; there will be only one opportunity to attend the memorial.”

The Avro Lancaster Mk III took off from RAF Fiskerton in Lincolnshire with a new crew from 49 Squadron, who knew they would have to complete 30 missions.

Its youngest member was Sergeant John Grenfell, the 19-year-old Air Gunner. The rest of the crew were aged between 20 and 23 and three of them were married: Knowles, Hardy and Waugh.

ND474 had already flown into Germany eight times before it was transferred to Pilot Officer Thomas Waugh and his colleagues.

Mrs Dexter, a member of the Squadron 49 Association, said: “Despite the terrible odds against them, the young crew of ND474 prepared to leave for Stuttgart, they had a meal together and collected their flying suits from the lockers rooms.

“The crew had only been together for a short time, but now they would be depending on each other to do their part and bring them all home.

“As the light faded ND474 rumbled down the runway, together with seventeen other Lancasters from 49 Squadron.

“Bomber Command mounted three raids that evening, the main raid to Stuttgart and the others to the railway yards at Amiens and an aeroplane engine factory at Woippy near Metz.

“Unbeknown to Bomber Command, the German Luftwaffe had found a way of locking on to the Lancaster’s radar system and this new technology was to prove fatal to many Lancaster crews.

“ND474 took off from Fiskerton at 7.05pm and was the third aircraft to leave the airfield.

“The main raid to Stuttgart consisted of 863 aircraft – 617 Lancasters, 230 Halifaxes and 16 Mosquitos, all from different squadrons based in Lincolnshire.

“At 8.05pm, five minutes after penetrating France, the German fighter controller had been alerted and had split his forces into two parts.

“The bomber force flew over France nearly as far as the Swiss frontier before turning north-east to approach Stuttgart.

“This delayed the German fighters contacting the bomber stream but, when the German fighters did arrive, just before Stuttgart was reached, the usual fierce combats ensued.

“At 11.15pm over Bolstern, south west of Saulgau, at a height of 6,200m, ND474 was intercepted by a German night fighter and shot down.

“Oberleutnant Gunther Koberich of 6./NJG2 claimed ND474 as his eleventh ‘Abschuss’ (aerial victory).

“The aircraft that Koberich flew on that night was a Junkers Ju88 C-6 equipped with SN2 radar.

“The entry in the Log of Achievements of Koberichs’ Radar Operator noted: ‘Attack from directly behind, fire in the port wing and fuselage. Crash observed. Victory confirmed. Contact on SN2.’

“ND474 had amassed just 97 hours on operational flying.”

Flight Officer Knowles’ aircraft was the only one from 49 Squadron to be lost and on the Stuttgart raid, Bomber Command lost in total 37 aircraft – 27 Lancasters and 10 Halifaxes, with two Lancaster bombers being forced to land in Switzerland.

Mrs Bexter said: “We now know that although ND474 was badly damaged with fire in the port wing and fuselage, the crew had tried to fly on to Switzerland.

“Realising that their aircraft wouldn’t make the journey home to Fiskerton, they turned towards the neutral country.

“Eighteen flying minutes from the Swiss border, ND474 crashed into a field near the village of Bolstern. All the crew were killed.”

If you have any information on the descendants of Flight Officer John Knowles, e-mail Mrs Dexter at louise.dexter@btinternet.com or 07717 536611

WHO WAS JOHN JOSEPH KNOWLES?

* Born February 1921

* Son of John James Knowles and Mary Minnie Knowles (nee Catlow)

* 23 at time of crash

* Married Toriye Knowles nee Kusumoto in Willesden in 1943

* Toriye was the daughter of Seyemon R Kusumoto (1895-1968) and Ada Florence Donaldson (aka Busbridge) (1894–1985)

* Ada, Toriye’s mother, was shown on electoral roll as living in 1946 in Paddock Road, Willesden

* In 1949, Toriye was also at this address along with an Eric J Busbridge

* In 1960 Toriye’s father was listed as a landscape architect in Station Road, Edgware

CREW OF ND474

* Pilot Officer Thomas William Waugh*, 23, of Hull, Yorkshire - Pilot

* Flight Officer John Joseph Knowles, 23, of Willesden - Bomb Aimer

* Flight Sergeant Terence McEneaney*, 22, of Waterford, Ireland - Navigator

* Sergeant William Hardy*, 22, of Maldon, Essex - Wireless Operator

* Sergeant Douglas Brigg Birbeck, 21, of Liverpool, Merseyside - Air Gunner

* Sergeant Ronald Hoole*, 20, of Mirfield, Yorkshire - Flight Engineer

* Sergeant John Grenfell Wise*, 19, of St Ives, Cornwall - Rear Gunner

* Families traced and to be represented at memorial service