ERT Madjitey was invited to an interview at the principals office at Achimota College. Together with his colleges Messrs. R.D. Ampaw and A. A. Laryea both old boys of Achimota College, he went through an interview conducted by Capt. R. W. H. Ballantine (who later became Commissioner of Police) in the presence of Principal Stopford. After this preliminary interview, Madjitey and his colleagues were invited to another interview at the Colonial Secretariat, presided over by the Colonial Secretary.

 On Monday the 10th of January, 1944 he reported to the Training school again and was directed to the medical officer, who after a short intelligence test, examined him medically and pronounced him fit for service in the Police Force. Madjitey was then sworn in as an enlisted recruit in the Ghana Police Service. The next six months were very difficult months at the Training Depot, but eventually E.R.T. Madjitey and his college R. D. Ampaw passed out and were both posted to Accra.

Following his promotion to Sub-Inspector, Madjitey was posted to Kumasi where he served for a year. There too it was hard going because as he found most of the European officers were opposed to any form of Africanization policy. This was however, understandable because they realized their prospects were greatly limited by the promotion of Africans to the senior ranks of the Police Force. Several obstacles were placed in his way but all to no avail and in May 1946 he started his upward climb in the Ghana Police Force with a government scholarship for the United Kingdom on attachment to the Lancashire Constabulary for a years course in General Police Duties....

On his return to the Gold Coast in May 1947, and after a few delaying tactics on the part of the authorities, E.R.T. Madjitey was eventually promoted to the gazetted rank of Assistant Superintendent of Police and posted to the port city of Takoradi where he served as an Immigration Officer. In August 1948, Madjitey was transferred to Accra to take charge of the B District and was concurrently appointed Honorary A.D.C. to the Governor of the Gold Coast. In 1949, Madjitey was transferred to Sekondi and in 1951 he was promoted to the Acting Rank of Superintendent of Police.

            In 1952 Madjitey once again proceeded to the United Kingdom to pursue the senior detective officers course in Scotland Yard. He returned to the Gold Coast in 1953 and was posted on a short relief duty to Tarkwa, but returned to Sekondi as second-in-command of the Western Region. On 1st December, 1953, Madjitey was promoted to the substantive rank of Superintendent of Police. In 1955 he attended the senior officers course at the Police Staff College at Ryton-on-Dunsmore at Coventry. On completion of this course he returned to the Gold Coast and was posted to Koforidua as second-in-command of the Eastern Region. In 1956, E. R. T. Madjitey took over full command of the Eastern Region with the acting rank of Chief Superintendent thus not only becoming the first Ghanaian but also the first African to take charge of a Police Region...

The same year Madjitey was nominated for the Colonial Commissioners course in Bramshill which he attended and on his return to the Gold Coast, was awarded a scholarship to the United States under the joint auspices of the United States International Education Program and the International Association of Chiefs of Police. While in the United States, Madjitey had sessions with several Police organizations, the FBI, CIA, Columbus City Police and the Grand Rapids Police. Madjitey returned to the Gold coast in March 1957 and participated Ghana's independence celebrations. On completion of the celebrations Madjitey took charge of Accra for some time and was later posted to Headquarters as Asst. Commissioner of Police. 

           On March 16th , 1958 Madjitey was appointed Deputy Commissioner of Police and on 9th October 1958, 
E. R. T. Madjitey was appointed Commissioner of Police
, thus becoming not only the first Ghanaian but also the first African in the whole of the British Commonwealth to head a Police Force. 

            ERT Madjitey served as Commissioner of Police from 1958 to 1964 [since the position of Inspector General of Police had reverted to Commissioner of Police] when following his opposition to Nkrumah's plan for disintegrating the Police Service under the guise of reorganization and his blunt refusal to be privy to the fabrication of evidence against Tawiah Adamafio, Ako Adjei and Cofie Crabbe, Nkrumah removed him and seven other senior officers from office, using (as pretext) an attempt a constable called Samuel Ametewe made on his life in circumstances which should have been obvious to the meanest sense that the Constable acted entirely on his own volition to avenge the wrong done to him by Nkrumah through the unlawful detention and persecution of three of his close relatives under the Preventive Dentention Act...