Raja Bongsu ibni Almarhum Sultan Muhammad Shah was also known as Raja Chik. After the demise of his brother, Almarhum Sultan Alauddin Mansur Shah Iskandar Muda, Raja Bongsu was installed as Sultan Ahmaddin Shah in 1786.
In 1795, the presence of the V.O.C. in Melaka had began to show a decline which led to the occupation of Melaka by the British, the first resident being Archibald Brown. In Perak, officers from the British East India Company along with a small detachment of British troops forced Christoffel Walbeehm, a V.O.C. commandant, to surrender the Dutch trading outpost of Tanjung Putus. By 1802, the trading of tin ore was largely taken over by the British East India Company.
In 1805, Perak was attacked by Sultan Ibrahim Shah of Selangor, as Sultan Ahmaddin perpetuated Perak’s pro-Dutch stance. The might of Perak was defeated and Sultan Ahmaddin Shah and his chiefs retreated upriver to Kuala Pelus. Sultan Ibrahim Shah had also warned the British presence at Tanjung Putus to leave Perak by virtue of Selangor’s presence from Sungai Kurau in the north down to Beting Beras Basah in the south.
Sultan Ahmaddin Shah ruled Perak for twenty years until his demise in Chegar Galah in 1806. The heir apparent to the throne, Raja Muda Mahmud ibni Raja Muda Ibrahim, the grandson of Marhum Muda Sultan Mahmud Shah, was described to be appointed Almarhum’s successor. It was also described that there was political turmoil amongst the Perak Rajas. To add to the problems, Raja Muda Mahmud refused to come to Sayong to allow the announcement of the new Sultan. This unfortunate turn of events had led to the body of Almarhum Sultan Ahmaddin Shah to remain uninterred for three months. Once it was decided that Almarhum’s son, Sultan Abdul Malik Mansur Shah, was to be installed, the cortege was finally brought downriver to Bota Kanan where Almarhum Sultan Ahmaddin Shah was interred. He was conferred the posthumous title of Marhum Bongsu.
Sultan Ahmaddin Shah was married to Toh Puan Puteh binti Laksamana Tok Kuala Bidor, Raja Tengah Bongsu binti Sultan Muzaffar Shah III, Che’ Sepiah binti Tok Imam Malikul Amin Ketior and Che’ Sakidah. He had issue from these wives, and his successor, Sultan Abdul Malik Mansur Shah, was Almarhum’s son from his marriage to Toh Puan Puteh. It is noted that the descendants of his sons from his other three wives became heirs presumptive in the Perak heir system, and in turn became Sultans themselves (for examples, Sultan Shahabuddin, Sultan Abdullah Muhammad Shah I and Sultan Ismail Mu’abidin Riayat Shah). Interestingly, the house of Sultan Abdullah Muhammad Shah II, Raja Muda Musa I and Sultan Idris I are all descended from Sultan Abdul Malik Mansur Shah.
 Following the installation of Sultan Abdul Malik Mansur Shah, Raja Muda Mahmud remained steadfast in his refusal to acknowledge to new Sultan. Raja Muda Mahmud, prior to Almarhum Sultan Ahmaddin’s demise, controlled Hulu Perak and this crisis effectively divided Perak into two. Historically, Selangor’s initial bond with Perak was with the marriages between the families of Marhum Muda and Raja Lumu, Sultan Ibrahim’s father. Support from Selangor to the faction siding with Raja Muda Mahmud added to the internal turmoil at that time. However, this crisis ended with Raja Muda Mahmud’s demise. The last descendant of Marhum Muda that was made heir presumptive was Raja Muda Mahmud’s son, Raja Radin, who was also made Raja Bendahara in 1826.