Towards the end of July 1957 the 'C' Company vacated Mannar Island and took over the Pooneryn Sector.Towards the end of July 1957 the 'C' Company vacated Mannar Island and took over the Pooneryn Sector.
The trial of the detainees arrested in regard of the attempted coup in 1962 was over by March 1965 and the soldiers guarding the suspects were returned to the Battalion. In April 1965, the whole Battalion shifted to Echelon Square, Colombo from the Race Course compound except the Officers' Mess which continued to remain at the Race Course. The buildings in at the Echelon Square were those that had been used by the Dutch as a hospital and as billets for soldiers by the British during the colonial times.
Captain MAP Samarasinghe joined the Regiment from the 1st Battalion Ceylon Light Infantry and took over command of the Headquarters Company relieving Captain NDHAB Silva who reported back to the 1st Battalion Ceylon Light Infantry before leaving the Army. In August 1965, having passed out from Army Training Centre Diyatalawa, 2nd Lieutenant B Jayasundara, 2nd Lieutenant MSM Nalim and 2nd Lieutenant A Ratnayake joined the Battalion. In September the same year, 2nd Lieutenant J Nammuni joined the Battalion after having passed out from the Pakistan Military Academy. He retired as a Major General in 1998 after holding a number of senior appointments in the Sri Lanka Army.
In October 1965, Major SB Miyanadeniya of the 1st Battalion Ceylon Sinha Regiment was appointed as the chief of the Sri Lankan Monitoring Team of the United Nations (UN) Peace Keeping Force which was employed in peace keeping duties related to the Indu-Pakistan War. Corporal Karunarathne KT was the first other ranker employed in UN Peace Keeping duties and did so in Congo. He was subsequently commissioned as a Quartermaster and eventually reached the Rank of Major (Quartermaster).
The Battalion took part in the Independence Day Parade held at Kurunegala in February 1966. As expected the performance of the Sinha troops was a major attraction for the crowd who had come to witness the parade and the day's celebrations.
In 1966, three new officers namely; 2nd Lieutenant GP Kulatunge, 2nd Lieutenant HA Somadasa and 2nd Lieutenant AG Weerasekara joined the Battalion. All these Officers held various field, senior staff as well as command appointments prior to retiring in the rank of Major General.
Lieutenant Colonel LHD de Silva relinquished Command of the 1st Battalion Ceylon Sinha Regiment on 5th March 1967 and Lieutenant Colonel ET de Z Abeysekera CLI took over the Battalion as its Officiating Commanding Officer. During this time a necessity arose to shift the Battalion to a place outside Colombo and thus shifted to the Police Training School at Katukurunda, Kalutara and the Police Training School was brought to Echelon Square in Colombo. The new location possessed a large extent of land and consisted of a training ground, parade square, billets, two large playgrounds and other basic requirements for training. It also had a cinema hall and 18 married quarters which made it advantageous for the Battalion's personnel. Additionally, it also had a paddy field and a coconut cultivation of nearly 10 acres. The taking over of a herd of 'Mura'buffaloes that produced good curd, poultry as well as a piggery enabled the Battalion to generate an income to the PRI (President, Regimental Institute) Account by running the farm.
There were also ample accommodation facilities for living-in personnel within the camp. Duty hours had to be curtailed because of the long distances 'living-out'personnel had to travel. Transport had to be provided for soldiers who performed guard duties at Army Headquarters Colombo and at other places of importance and for platoons employed on 'internal security' duties in Colombo and its suburbs. Though there was present considerable uneasiness among the members of the Battalion the Commanding Officer of the Battalion toiled hard to take up this challenge and ameliorate whatever difficulties the change of location caused. On 30th April 1968, Lieutenant Colonel ET de Z Abeysekara relinquished his duties of the Battalion as its Commanding Officer'
Lieutenant Colonel TSB Sally took over duties as the Commanding Officer on 1st May 1968. Being the first Adjutant of the Battalion thus, one of its pioneers he took much pain to uplift the standard of the Regiment. It was the first time that a pioneer of the Regiment to have been appointed as the Commanding Officer of the Battalion. His sound knowledge of military law and flair to instruct made it easy for him to impart knowledge to officers and other ranks of the Battalion. Lieutenant Colonel Sally contributed much towards the welfare of officers and other ranks. He opened within the camp a cooperative store, officially approved by the Department of Co-operatives with Battalion personnel as its members. Further, a loan scheme was offered to those who lived in married quarters to purchase furniture of their choice on an easy payment scheme.
Lieutenant Colonel TSB Sally left for America to follow two courses on personnel and financial management, each of 8 months duration. In his absence, Major CC Labrooy, the Second in Command of the Battalion overlooked duties of the Commanding Officer. After returning from the USA in 1969 Lieutenant Colonel TFB Sally resumed duties as Commanding Officer.
In 1969, two soldiers of the Gemunu Watch were killed and buried in the beach in Mannar by unidentified persons. The soldiers of the Sinha Regiment who were stationed at Thalladi Camp, provoked by this incident, attacked the villagers of Thalvapadu. The police, brought to control the situation had to open fire and shot at a Sinha Regiment soldier named Yapa. He was admitted to the Anuradapura Hospital where part of his leg was amputated. Consequently, the Battalion was relieved from TaFII duties and sent back to Kalutara.
In May 1970 the General Election saw a change in political power. Following incidents of civil unrest officers and other ranks of the Regiment were deployed in Colombo and in the up-country areas to maintain law and order.
