He was appointed Officer-in-Charge (OiC) Intensive Flying Trials Unit (IFTU) and trained in Russia.

Theophilus was the commissioning commanding officer and was the first Indian Pilot to land MiG-29K on the aircraft carrier INS Vikramaditya (R33).

[3] In the rank of Commodore, Theophilus headed the directorate of air warfare and flight safety (AWFS) at Naval Headquarters.

[4][5] On 1 April 2022, Theophilus was promoted to flag rank and appointed Deputy Commandant (DepCom) and Chief Instructor of the Indian Naval Academy, Ezhimala.

[6][7] After a fourteen-month long stint as DepCom of INA, he was appointed Flag Officer Naval Aviation (FONA).