After the fall of France, there were still a substantial number of DB-7s which had not yet been delivered to the Armee de l'Air. On June 14, the United Kingdom agreed to take over the DB-7 order, including those aircraft intended for Belgium. The first diverted DB-7s began to arrive in Britain during August of 1940.
The early DB-7s powered by 1000 hp R-1830-SC3-G engines were designated Boston I. A total of 130 DB-7s are listed on RAF rolls as Boston I, with RAF serials being AE457 to AE472, AX848 to AX851, AX910 to AX918, AX920 to AX975, BB890 to BB912, BD110 to BD127, and DK274 to DK277. Unfortunately, the final batch (DK274/DK277) arrived in damaged condition and had to be stricken off strength. The throttles of these French machines had to be modified so that their operation was reversed--being pushed forward to open rather than close as was the French fashion. These Boston Is were considered as being unsuitable for combat, and were restricted to training and other non-operational duties.
The ex-French contract DB-7s powered by the more-powerful 1100 hp R-1830-S3C4-G engines (first introduced on the 131st DB-7) equipped with two-speed superchargers were temporarily designated Boston II. RAF serials were AW392 to AW414, BJ458 to BJ501, BK882, BK883, BL227, BL228, BT460 to BT465, BV203, DG554, and DG555.
The French had originally intended to use the DB-7 as a short-range tactical attack aircraft. Consequently, these former French machines all had too short a range for the RAF to be able to use them as light bombers against German targets in Europe. It just so happened that the RAF was at that time in desperate need of an aircraft suitable for night fighting and intruder duties and which was also capable of carrying the heavy and cumbersome airborne interception radar that was available at the time. The Boston II had a good performance and had a large fuselage and appeared to fit the bill. The decision was made to modify most of the Boston II aircraft (as well as some Boston I aircraft which had been reengined) for night intruder and night fighting duties. These conversions were initially known as Ranger by the RAF, but were eventually named Havoc I.
There were two basic versions of the Havoc I, an Intruder version with a three-man crew, a glazed nose, five 0.30-inch machine guns, and 2400 pounds of bombs, and a Night Fighter version with an early AI Mk.IV radar, a two-man crew, and eight 0.30-inch machine guns.
The first Boston II -> Havoc I conversion was carried out by the Burtonwood Aircraft Repair Depot, Liverpool, during the winter of 1940/41. More than a hundred of these conversions were completed during the next few months. In all, 181 Boston aircraft were converted to Havoc I configuration. Included in this total were some Boston I aircraft which had been reengined. Serials were AW392 to AW414, AX848, AX851, AX910 to AX918, AX921, AX923, AX924, AX930, AX936, AX974, AX975, some from AE457/AE472, BB891 to BB895, BB896 to BB904, BB907 to BB909, BB91, BB912, BD110 to BD127, BJ458 to BJ501, BK882, BK883, BL227, BL228, BT460 to BT465, BV203, DG554, DG555.
The Intruder version of the Havoc I was painted all black and was equipped with flame-damping exhausts for night operations. It featured armor protection for its three crew members and it was equipped with four forward-firing 0.303-inch Browning machine guns in the lower part of the glazed fuselage nose, plus a single 0.303-inch Vickers flexible machine gun in the rear cockpit. A bomb load of up to 2400 pounds could be carried. The night intruders were extremely useful in their intended role, and caused considerable damage to many German targets on the Continent. Operating at night and at low altitude, they were difficult to intercept and carried a hefty punch with their 2000-pound bombload and battery of four 0.303-inch nose machine guns.
For pure night fighting duties, the Havoc I was fitted with a "solid" nose housing an additional four 0.303-inch guns and carrying the AI Mk.IV radar. A crew of two was carried, the radar operator sitting in the rear cockpit. There were no provisions for rear-defense machine guns or for bombs. Some Havoc I Night Fighters were fitted with a Boulton-Paul nose carrying a battery of no less than 12 0.303-inch machine guns.
The first of these Havoc Is entered service with No. 85 Squadron of the RAF on April 7, 1941. Havocs subsequently also served with No. 25 and 92 RAF Squadrons.
Number 92 Squadron received twenty modified Havoc I (Pandora) intruder aircraft, the name "Pandora" being a code name for the Long Aerial Mine (LAM) which was an explosive charge towed by a 2000-foot length of cable stowed in the bomb bay of the Havoc. The LAM was trailed in the path of enemy aircraft in the hope of scoring a hit. Serials of Boston aircraft known to have been equipped with this device include AX913, BK883, BT465, and DG554. This device was not very successful, and only one victory was attributed to this system. No 92 Squadron was disbanded in November of 1941, and the "Pandora" Havocs were converted back to Intruder configurations.
Havoc I Turbinlite was the name given to a night fighter version which was modified to carry a 2.7 million candlepower Helmore/G.E.C. searchlight in the nose in addition to the AI radar. The system was the brainchild of Wing Commander W. Helmore, and was built by the General Electric Company. It was intended that this searchlight would operate in conjunction with the AI radar. The radar would be used to locate enemy night intruders, and the aircraft's radar controller would direct the pilot to close to within 3000 feet of the target. The spotlight would then illuminate the target so that accompanying fighters could attack it. Thirty-one such Turbinlite conversions were made. Serials of Havoc aircraft known to have been equipped with the Turbinlite included AX913, AX924, AX930, BB897, BB899, BB907/BB909, BD100, BD111, BD120, AW392, AW393, AW400, AW401, AW404, AW406, AW411, AW412, BJ460, BJ461, BJ467, BJ469, BJ470, and BK882.
Since the nose and the bomb bay were now full of equipment, the Turbinlite Havoc was unarmed and depended on accompanying fighters to destroy the targets which it was supposed to illuminate. This mode of attack was not all that successful, since the glaring searchlight gave enemy defensive gunners something bright to fire at. The development of centrimetric radar made such tactics obsolete, and the Turbinlite Havoc units were soon disbanded,
The following serials were transferred to the USAAF: AX913, AX922,
BB891, BB896, AW394, AW400, AW403, BJ461, BJ466, BJ473, BJ488, BJ499,