The Royal Air Force (RAF) was an early customer for the B-25 via Lend-Lease. The RAF was the only force to use the B-25 on raids against Europe from bases in the United Kingdom. The USAAF used the Martin B-26 Marauder for this purpose instead.
The first Mitchells to reach the RAF were 23 B-25Bs which were designated Mitchell I by the RAF and assigned the RAF serials FK161 through FK183. They were delivered in August 1941, and were assigned to No 111 Operational Training Unit based in the Bahamas. These planes were used exclusively for training and familiarization and never achieved operational status.
The first operational B-25s to serve with the RAF were B-25Cs and Ds, which were designated Mitchell II by the RAF. The first operational B-25s for the RAF were a batch of B-25Cs. Some of these were used by No. 13 OTU in England, but again most of them went to No. 111 OTU in the Bahamas. A total of 93 Mitchell Is and IIs had been delivered to the RAF by the end of 1942. The Mitchell II served with No. 2 Group, the RAF's tactical medium bomber force. These planes were assigned to Nos 98, 180, 226 and 329 Squadrons.
The first RAF operation with the Mitchell II took place on January 22, 1943, when six aircraft from Nos 98 and 180 Squadron attacked oil installations at Ghent. Things did not go well at all that day. Flak over the target shot down one Mitchell, and Luftwaffe FW 190s pounced on the formation and shot down two more. Since they figured that they must be doing something wrong, the RAF Mitchell squadrons stood down to improve their tactics. They had to develop extremely tight formations in order to concentrate their bombs and to ward off enemy fighters. The RAF Mitchells generally retained the retractable ventral turret, since protection from below was absolutely essential for medium-altitude operations over Europe.
The RAF Mitchells returned to action on May 13. After the invasion of Europe, all four Mitchell squadrons moved to bases in France to support Allied ground forces. The British Mitchell squadrons were joined by No. 342 (Lorraine) Squadron of the French Air Force in April of 1945.
Altogether, 167 B-25Cs and 371 B-25Ds were delivered to the RAF as Mitchell II. Twelve RAF serial number batches were allocated to the Mitchell II.
The Mitchell II was also issued to No. 320 (Dutch) Squadron in September of 1943. This squadron had been formed in June 1940 from personnel of the Royal Dutch Naval Air Service who had fled to England following the occupation of Holland by the Germans. They carried out operations in Europe against gun emplacements, railway yards, bridges, troops, and other tactical targets. 320 Squadron moved to Belgium in October 1944 and flew tactical missions from there until VE Day.
No 305 (Polish) Squadron flew Mitchell IIs from September to December 1943 before transitioning to Mosquitos.
The RAF was allocated 316 B-25Js as Mitchell IIIs. Deliveries took place between August 1944 and August of 1945. However, only about 240 of these planes actually reached Britain, with some being diverted to No. 111 OTU in the Bahamas, some crashing during delivery and some being retained in the USA.
The Mitchell IIIs that did reach Britain were issued as replacement aircraft for 2 Group's Mitchell IIs from November 1944, although two Group squadrons retained the Mk II since they regarded it as having a better control response than the Mk III because it was lighter.
On January 1, 1945, No. 80 Squadron lost 13 Mitchells on the ground during the Luftwaffe's New Year's Day raid on Allied airfields on the Continent.
In addition to the 2nd Group, the B-25 was used by various second-line RAF units in the UK and abroad. In the Far East, No. 3 PRU, which consisted of Nos. 681 and 684 Squadrons, flew the Mitchell (primarily Mk IIs) on photographic reconnaissance sorties.
The Mitchell II and II soldiered on into the post-war period, there still being 393 Mitchells on RAF rolls as late as December 1945.
A total of 910 B-25s went to Britain under Lend-Lease, but some were returned at the end of the war. Unfortunately, the correlation between RAF and USAAF serials is largely unknown.
FK161/FK183 Mitchell I (B-25B) FL164/FL218 Mitchell II (B-25C) FL671/FL709 Mitchell II (B-25C) FL851/FL874 Mitchell II (B-25C) Delivery of FL859 only confirmed FR141/FR207 Mitchell II (B-25C) allotments to Dutch forces as follows: FR141/FR145 FR156/FR157 FR159/FR161 FR163 FR168/FR171, FR190/FR200 FR208/FR209 Mitchell II (B-25G) FR362/FR384 Mitchell II (B-25C) FR393/FR397 Mitchell II (B-25C) FV900/FV939 Mitchell II (B-25D) FV940/FV999 Mitchell II (B-25C) FW100/FW280 Mitchell II (B-25D) FW220, FW237, FW246, FW251, FW259, FW260, FW272, FW274, FW278/FW280 held in Canada for RCAF HD302/HD345 Mitchell II (B-25D) HD310,H/HD315, HD317/HD320, HD322/HD326, HD221/HD335, HD337/HD345 retained in Canada for RCAF KL133/KL161 Mitchell II (B-25D) MA956 Mitchell II (B-25C) ex Dutch MA957 Mitchell II (B-25C) crashed at sea Nov 1944. HD346/HD400 Mitchell III(B-25J) KJ561/KJ800 Mitchell III(B-25J) KJ774, KJ777/KJ783, KJ785, KH787/KJ792, KJ795/KJ799 diverted to USAAF. KP308/KP328 Mitchell III(B-25J) - all returned to USA