Jarvis served in 2 SAAF Squadron between 11 November and 4 December 1940 and was then posted to 1 SAAF Squadron.

At 14:00 on 29 January, 1 SAAF Squadron took off to attack Gura, with six Hurricanes (Major Lawrence Wilmot, Captain K. W. Driver, Lieutenants John Hewitson, Andrew Duncan, Hendrik Johannes Piet Burger and Leonard le Clues Theron) flying as top cover to five Gladiators, which would strafe. As they approached the Hurricanes run into several S.79s and a large number of CR.42s, which were seen over the airfield, the bombers having just returned from a raid over the front, and the fighters having scrambled at the approach of the South African aircraft. Captain Driver at once attacked an S.79 as it was going in to land, and shot it down in flames, two members of the crew baling out. The Gladiators then arrived, led by Captain Brian Boyle. These also met the Fiats, Lieutenant H. P. Smith (Gladiator N5851) and Lieutenant Jarvis each claiming one shot down.
Capitano Antonio Raffi, commander of the 412^a Squadriglia, was above with two of his pilots, Tenente Luciano Cacciavillani and Maresciallo Aroldo Soffritti (they scrambled at 15:20), and he saw the Hurricane shoot down the S.79 before he could intervene. He then spotted the Gladiators, which he believed to be six strong, and at once, a great dogfight begun, during which the South Africans saw many Fiats falling away. Driver meanwhile had seen Adi Ugri landing ground on which four S.81s were dispersed, and attacking these, he left one (claimed as a S.79) in flames.
On return to base the combat with the Fiats was fully discussed, and it was decided that five had been shot down, one each by Lieutenant Smith and Lieutenant Jarvis, the other three being impossible to allocate to individual pilots. All the SAAF aircraft returned safely, although one Gladiator (N5831) had been hit by a single bullet.
This proves how easy it was to overestimate the damage caused, and indeed the numbers involved, in a whirling dogfight. Although several CR.42s were hit and damaged, none was in fact shot down. Tenente Cacciavillani's CR.42 was badly damaged by 50 hits, and Maresciallo Soffritti's was also damaged. Capitano Raffi’s own aircraft was hit five times and he recorded that he took ten bullets in his parachute and lost the fabric in the fuselage close to the cockpit and the tail plane. It seems that Raffi’s fire hit and damaged Lieutenant Smith Gladiator, who landed unhurt. The Italians reported combat against four Hurricanes and six Gladiators and reported one Gladiator shot down. Tenente Cacciavillani fired 60 rounds of 7.7mm, and claimed a Gladiator probably destroyed (shared) (strangely enough, this claim has been cancelled by a pen line in his logbook).

Air reconnaissance had reported that new CR.42s being assembled at Massawa after delivery by transport aircraft, and at 08:00 on 21 February, Major Lawrence Wilmot from 1 SAAF Squadron took off from Kassala with Captain Brian Boyle and Lieutenants Robin Pare, John Coetzer, Leonard le Clues Theron, Servaas de K. Viljoen and Jarvis. The Hurricanes refueled en route at Agordat and took off at 11:00, attacking Massawa an hour later. A small number of aircraft was seen outside the hangars, but the number inside was not known, so all six hangars were attacked, the pilots approaching at zero feet and firing directly into them; all were left in flames, the roof of one being blown right off by Major Wilmot. Six Ca.133s and a CR.42 were strafed in the open, and claimed in flames, while Lieutenant Robin Pare wiped out an anti-aircraft position and crew, which were firing on Major Wilmot. His guns then jammed but he continued to make dummy runs on the AA posts, being the last to leave the area. Lieutenant Coetzer was however shot down and killed by AA fire, his Hurricane (V7658) was seen crashing in flames.
In fact, three Ca.133s and two S.81s, all of which had been damaged the previous day, were destroyed, and one more of each was damaged.

On 23 February 1941, seven Hurricanes of 1 SAAF Squadron flew forward to Tole where they refueled. At noon, Major Lawrence Wilmot (V7733?) led Captain Brian Boyle and Lieutenant Andrew Duncan to strafe Makele airfield while Captain K. W. Driver, Lieutenant Servaas de K. Viljoen, Lieutenant Jarvis and Lieutenant Leonard le Clues Theron provided top cover to the Vickers Wellesley acting as the navigation leader and which was intended to distract the Italians from the three low-flying Hurricanes as they went in. However, the RAF bomber lost its way soon after take-off, being dutifully followed by the top cover formation. In the target area, Major Wilmot realised that something was wrong when he saw a rising dust cloud to his left. He led his two companions toward this.
Finding Makele, the trio went in to strafe. Major Wilmot set fire to a CR.32, which was on the ground with its pilot Sottotenente Vincenzo Forcheri of the 410^a Squadriglia in the cockpit, about to take off. He leapt out under fire and managed to reach a trench.
Without their top cover, the Hurricanes were vulnerable to surprise attack, and at that moment reportedly three CR.32s arrived (the dust had been the sign of their scramble). Two fled but Sottotenente Alberto Veronese made good use of their advantageous position and dived on Major Wilmot’s aircraft, shooting it down. Lieutenant Duncan was on him like a flash and shot him down in flames. Veronese managed to parachute to safety, slightly wounded.
Wilmot had in the meantime carried out a crash-landing after that his Hurricane had been hit in the radiator, and became a POW.
Captain Driver, leading the four top-cover Hurricanes, now saw smoke rising, and dived down to join the strafing, the formation claiming five S.79s and three CR.32s set on fire and three S.79s as damaged.

Jarvis ended the war with 1 biplane victory.

Post-war he served in the RAF and retired in Dorset, England.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1941
1	29/01/41	15:20-	1	CR.42 (a)	Destroyed	Gladiator II		Gura airfield	1 SAAF Squadron
	21/02/41	12:00-	1/7	Ca.133 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	12:00-	1/7	Ca.133 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	12:00-	1/7	Ca.133 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	12:00-	1/7	Ca.133 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	12:00-	1/7	Ca.133 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	12:00-	1/7	Ca.133 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	21/02/41	12:00-	1/7	CR.42 (b)	Shared destroyed on the ground	Hurricane		Massawa	1 SAAF Squadron
	23/02/41	p.m.	1/4	S.79	Shared destroyed on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	S.79	Shared destroyed on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	S.79	Shared destroyed on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	S.79	Shared destroyed on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	S.79	Shared destroyed on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	CR.32	Shared destroyed on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	CR.32	Shared destroyed on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	CR.32	Shared destroyed on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	S.79	Shared damaged on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	S.79	Shared damaged on the ground	Hurricane		Makele airfield	1 SAAF Squadron
	23/02/41	p.m.	1/4	S.79	Shared damaged on the ground	Hurricane		Makele airfield	1 SAAF Squadron

Biplane victories: 1 destroyed.
TOTAL: 1 destroyed, 15 shared destroyed on the ground, 3 shared damaged on the ground.
(a) Claimed in combat with 3 CR.42s from the 412^a Squadriglia, which all were damaged but no losses were suffered. 1 SAAF Squadron claimed 5 CR.42s while suffering 1 lightly damaged Gladiator.
(b) Three Ca.133s and two S.81s, all of which had been damaged the previous day, were destroyed, and one more of each was damaged.

Sources:
Luciano Cacciavillani's personal logbook courtesy of Cacciavillani family (Luciano jr and Alberto)
Dust Clouds in the Middle East - Christopher Shores, 1996 Grub Street, London, ISBN 1-898697-37-X
Springbok Fighter Victory: East Africa Volume 1 1940 – 1941 – Michael Shoeman, 2002 African Aviation Series No. 11, Freeworld Publications CC, ISBN 0-958-4388-5-4
Additional info kindly provided by Stefano Lazzaro, Michele Palermo and Ludovico Slongo.