Luftwaffe attacks on the Fleet anchorage at Scapa Flow led to the Royal Navy forming 804 Squadron.
On 25 November 1939, four Sea Gladiators of 769 Squadron were detached to Hatston on Orkney and, on 30 November, the detachment became 804 Squadron. Petty Officer Theobald served with this unit.
The Squadron was at this time under Fighter Command’s control and remained so during the Battle of Britain period.
Lieutenant Commander John Cockburn took command of 804 Squadron on 9 December.

During the day on 10 April 1940, Luftwaffe reconnaissance aircraft had spotted the British Home Fleet as well as two convoys to the south of the Orkneys. In the early evening several He 111s and Ju 88s attacked these ships.
804 Squadron’s diary describes the events:

“A tremendous day for HMS Sparrowhawk [RNAS Hatston], the first and we hope by no means the last. No.804 began their fun at 1605 hours when Yellow Section flew off to Copinsay. At 1645 hours Red Section were sent to patrol between Copinsay and Burray. As soon as they got there, Red saw a Heinkel IIIK about 10 miles east going north east. Hot pursuit was begun and as the Section followed, Hurricanes could be seen gathering on the cloud, dodging Heinkel’s tail. No.43 Squadron had done their job. At 2045 the evening the blitzkrieg began.
Red were scrambled to Copinsay and e/as were reported approaching from the east at 20,000ft, so Red patrolled at 18,000ft. By 2100 hours all sections were in the sky and the party had started, the guns putting up an ugly barrage. Yellow had the first chase after an e/a which was in a long dive towards Kirkwall and which peppered Kirkwall and Hatston with front guns. Red chased after another, and during this party Blue Section came galloping up on seeing the shooting. Plenty of e/a were coming, so “Smee” chose a back one and stuffed himself under its tail. He and his section rattled away with such good effect that the e/a was last seen in a flat right hand spiral going down toward South Ronaldsay.”

"Blue leader was on patrol with his section of 3 a/c at 10,000 feet to the East of Burray. Weather was clear and good visibility with 5/10 cloud at 7,000 feet in a large bank. Blue leader was one mile off Burray when at 2120 hours, he was attracted by machine gun fire to the south and saw an E/A travelling west towards Scapa Flow at about 200 m.p.h. some 500 feet above him. The E/A appeared to be machine gunning searchlight positions from his from gun.
There was a second aircraft in formation but as soon as Blue Leader climbed under the first E/A's tail to attack, the second E/A broke away and was not seen again.
Blue Leader closed rapidly and opened fire at from 350 to 250 yards closing to about 100 yards. This was repeated four times the attacks being delivered from either dead astern or over the port or starboard quarter. Each attack consisted of one burst of about 6 seconds. Tracer was observed to be entering the fuselage of E/A; tracer bullets were seen from both top and lower rear guns.
After Blue Leaders first attack lower gun was silenced but top gun continued to fire. Throughout the attacks E/A performed a series of violent turns necessitating deflection allowance by Blue leader. Towards the end of the fourth attack, E/A started to lose height.
Blue 2 now dived to attack and fired 1000 rounds from astern by which time E/A was in a flat right hand spiral dive. Having lost formation Blue 2 landed at Wick. Blue 3 did not get an opportunity to fire as Blue 1 and 2 were conducting their attack from astern. But he saw the starboard engine was disabled with clouds of smoke issuing from it and followed till the E/A's dive become too fast for him to follow any more.
Some slipstream was noticed when at close range and at some stage in the combat a bullet of rifle calibre passed through a spar of port main plane. In all Blue leader fired 2,600 rounds and experienced no stoppages. The R/T was not working very well either from the ground or between pilots owing to jamming interference.
No cine camera gun was carried and it was to dark to distinguish any marking or the type of plane, though it was thought to be a Heinkel IIIK.
Blue Leader landed at Hatston at 2204 hours."

Theobald ended the war with 1 shared biplane victory.

Claims:

Kill no.	Date	Time	Number	Type	Result	Plane type	Serial no.	Locality	Unit
	1940
	10/04/40	21:20	1/3	He111 (a)	Shared destroyed	Sea Gladiator		1m E Burray	804 Squadron

Biplane victories: 1 shared destroyed.
TOTAL: 1 shared destroyed.
(a) Probably claimed in combat with He 111s from 1/KGr. 100, which suffered one aircraft badly damaged but succeeded in getting back with one wounded aboard. 804 Squadron claimed two He 111s.

Sources:
Fledgling Eagles - Christopher Shores with John Foreman, Christian-Jaques Ehrengardt, Heinrich Weiss and Bjørn Olsen, 1991 Grub Street, London, ISBN 0-948817-42-9
Gloster Gladiator Home Page - Alexander Crawford
Those Other Eagles – Christopher Shores, 2004 Grub Street, London, ISBN 1-904010-88-1