RAF Mustang Mk.Is did not escort Wellingtons on a raid to the Dortmund-Ems Canal in October 1942. The facts are that the four Mustang Mk.I aircraft of No.268 Squadron conducted their sortie some 12 hours before the Wellingtons conducted their sortie that night over the same area. The confusion and connection of the two sorties arises from multiple editing of the original RAF Official Communique for that day which lists the two sorties separately, the communique then being edited for transmission from the UK to the USA (reducing the word count) and then a further editing by the releasing press agency that released the details to the various news services in the USA that merged the two distinct operations into one. That was then printed in multiple US newspapers at the time. Those press releases were what was then found as a source of information by researchers/authors of a number of early books on the history of the Mustang and have been repeated as fact ever since.
The Squadrons of Army Co-operation Command did in fact, conduct a number of long range bomber escort operations in late 1942 into early 1943. The first of these was escorting the Bostons of No.88 Sqdn RAF on a low level attack against Den Helder in the Netherlands on 16 September 1942. The sortie was conducted at low level throughout, so the Mustangs were well suited to the low level transit and attack at low level with the Bostons. No Bostons or Mustangs lost in the attack. (Photos of this operation held in collection of IWM London.) Further longer range low level bomber escort sorties were conducted by various ACC Mustang Mk.I squadrons into early 1943, primarily for the Boston and Ventura units of 2 Group. Regularly, it is reported in the post action combat report, that the allocated Spitfire escorts either turned up late to the departure rendezvous point, did not turn up at all (did not make the rendezvous) or left early from the escort due to fuel shortage issues. The Mustangs got a good reputation with the 2 Group bomber units for turning up on time and at the rendezvous point and staying with the bombers. However, the ACC Mustang units were then removed from the close escort role - RAF wartime file notes suggest a bit of politics at play - and were then instead used to conduct diversionary operations in support of low level bomber raids by units of 2 Group. So they would be tasked to conduct Rhubarbs or Rangers slightly ahead of the bomber raid to attempt to draw enemy fighters away from where the bombers would be.
Squadrons in ACC were well aware of the long range potential of the Mustang Mk.I and had been conducting long range navigation exercises for some time working out the best engine settings to get best usable combat range out of the aircraft. As an example in mid 1942, a flight from RAF Snailwell near Haymarket in East Cambridgeshire at low altitude to the vicinity of Edinburgh, battle climb to 10,000 to 15,000ft, fifteen minutes simulated air combat at high engine power and high fuel consumption, then return to Snailwell with ample reserves. And course chosen was not a straight line between the two but included flight out over the North Sea and Irish Sea down and back to properly simulate a long approach over water to the target area and the usual 'feints' to throw off radar.
By mid-1943, the reconnaissance requirements for the invasion were developing and so the change in focus occurred, then the Mustang Squadrons, by that time ACC had been disbanded and the Squadrons were attached to Fighter Command pending the formal formation of 2TAF, tasking shifted to coverage of required reconnaissance targets with Rhubarbs on an opportunity basis. Added to the D-Day commitments, they then were tasked with low level coverage of suspected V weapon sites, that escalated in early 1944 to include pre-and post bombing low level photographic coverage of V weapon sites. That was primarily with the Mustang Mk.I and Mk.IA given the timeframe.
RAF Mustang Mk.IIs, since they only got 50 of them as replacements for the P-51/Mustang Mk.IAs they had not earlier received, were not going to be in significant enough numbers for use other than attrition replacements for the earlier Mustang Mk.I and Mk.IAs. They arrived, crated in the UK from USA, recorded arrivals from early June to end of July 1943. First recorded issue to an operational Squadron, being No.II(AC) Squadron, late April 1944, with aircraft being issued through May 1944 into beginning of June 1944. As such by time of D-Day the Squadron did not have sufficient operational Mk.IIs to meet its operational commitments for the invasion and had to borrow Mustang Mk.IAs from No.268 Sqdn until about the end of June 1944.
The RAF Mustang Mk.III squadrons were initially used in a fighter bomber role in the lead up to and immediately after D-Day. That role came as a bit of a surprise to the RAF aircrew involved at the time, but a clue to that thinking at the time, was the number of ex-ACC Squadron Mustang pilots being posted to the Fighter Command Mustang Mk.III Squadrons at the time. Part of the thinking regarding this at the time was the load and range consideration, the Mustang being able to haul a heavier bombload over a longer distance compared to the Spitfire and Typhoon. So they got the targets furtherest from the UK airfields. Once the Allies were well established on the Continent and aircraft range with a bombing payload became less of an issue, and Spitfire units could be based on the Continent, the Mustang Mk.III Squadrons were transferred from 2TAF to Fighter Command, being replaced by Spitfire units transferred from Fighter Command to 2TAF. The RAF Mustang MK.III units then worked up to provide bomber escort for USAAF and RAF bombers. That then became the primary function of the RAF Mustang Mk.III units until VE-Day.
There is a book out due in June 2020 that looks at the history of the N.A. P-51/B/C Mustang in the context of the development of the USAAF long range bomber escort requirement and the development of the Mustang, published by Osprey, authored by William James Marshall and Lowell Ford (no relation), with input from the like of Gruenhagen and a broad community of Mustang specialist researchers/authors/current restorers and operators, and draws heavily on lots of original source documentation.
The Squadrons of Army Co-operation Command did in fact, conduct a number of long range bomber escort operations in late 1942 into early 1943. The first of these was escorting the Bostons of No.88 Sqdn RAF on a low level attack against Den Helder in the Netherlands on 16 September 1942. The sortie was conducted at low level throughout, so the Mustangs were well suited to the low level transit and attack at low level with the Bostons. No Bostons or Mustangs lost in the attack. (Photos of this operation held in collection of IWM London.) Further longer range low level bomber escort sorties were conducted by various ACC Mustang Mk.I squadrons into early 1943, primarily for the Boston and Ventura units of 2 Group. Regularly, it is reported in the post action combat report, that the allocated Spitfire escorts either turned up late to the departure rendezvous point, did not turn up at all (did not make the rendezvous) or left early from the escort due to fuel shortage issues. The Mustangs got a good reputation with the 2 Group bomber units for turning up on time and at the rendezvous point and staying with the bombers. However, the ACC Mustang units were then removed from the close escort role - RAF wartime file notes suggest a bit of politics at play - and were then instead used to conduct diversionary operations in support of low level bomber raids by units of 2 Group. So they would be tasked to conduct Rhubarbs or Rangers slightly ahead of the bomber raid to attempt to draw enemy fighters away from where the bombers would be.
Squadrons in ACC were well aware of the long range potential of the Mustang Mk.I and had been conducting long range navigation exercises for some time working out the best engine settings to get best usable combat range out of the aircraft. As an example in mid 1942, a flight from RAF Snailwell near Haymarket in East Cambridgeshire at low altitude to the vicinity of Edinburgh, battle climb to 10,000 to 15,000ft, fifteen minutes simulated air combat at high engine power and high fuel consumption, then return to Snailwell with ample reserves. And course chosen was not a straight line between the two but included flight out over the North Sea and Irish Sea down and back to properly simulate a long approach over water to the target area and the usual 'feints' to throw off radar.
By mid-1943, the reconnaissance requirements for the invasion were developing and so the change in focus occurred, then the Mustang Squadrons, by that time ACC had been disbanded and the Squadrons were attached to Fighter Command pending the formal formation of 2TAF, tasking shifted to coverage of required reconnaissance targets with Rhubarbs on an opportunity basis. Added to the D-Day commitments, they then were tasked with low level coverage of suspected V weapon sites, that escalated in early 1944 to include pre-and post bombing low level photographic coverage of V weapon sites. That was primarily with the Mustang Mk.I and Mk.IA given the timeframe.
RAF Mustang Mk.IIs, since they only got 50 of them as replacements for the P-51/Mustang Mk.IAs they had not earlier received, were not going to be in significant enough numbers for use other than attrition replacements for the earlier Mustang Mk.I and Mk.IAs. They arrived, crated in the UK from USA, recorded arrivals from early June to end of July 1943. First recorded issue to an operational Squadron, being No.II(AC) Squadron, late April 1944, with aircraft being issued through May 1944 into beginning of June 1944. As such by time of D-Day the Squadron did not have sufficient operational Mk.IIs to meet its operational commitments for the invasion and had to borrow Mustang Mk.IAs from No.268 Sqdn until about the end of June 1944.
The RAF Mustang Mk.III squadrons were initially used in a fighter bomber role in the lead up to and immediately after D-Day. That role came as a bit of a surprise to the RAF aircrew involved at the time, but a clue to that thinking at the time, was the number of ex-ACC Squadron Mustang pilots being posted to the Fighter Command Mustang Mk.III Squadrons at the time. Part of the thinking regarding this at the time was the load and range consideration, the Mustang being able to haul a heavier bombload over a longer distance compared to the Spitfire and Typhoon. So they got the targets furtherest from the UK airfields. Once the Allies were well established on the Continent and aircraft range with a bombing payload became less of an issue, and Spitfire units could be based on the Continent, the Mustang Mk.III Squadrons were transferred from 2TAF to Fighter Command, being replaced by Spitfire units transferred from Fighter Command to 2TAF. The RAF Mustang MK.III units then worked up to provide bomber escort for USAAF and RAF bombers. That then became the primary function of the RAF Mustang Mk.III units until VE-Day.
There is a book out due in June 2020 that looks at the history of the N.A. P-51/B/C Mustang in the context of the development of the USAAF long range bomber escort requirement and the development of the Mustang, published by Osprey, authored by William James Marshall and Lowell Ford (no relation), with input from the like of Gruenhagen and a broad community of Mustang specialist researchers/authors/current restorers and operators, and draws heavily on lots of original source documentation.