Halin has attracted over a century of scholarship, and is generally acknowledged as the foundation stone of Myanmar’s historical civilisation. The Pyu cities of Sriksetra, Beikthano and Halin were inscribed on the UNESCO World Heritage list in 2014, with Halin, at c. 540 hectares, the smallest by some margin. Halin, however, was notable for its extensive prehistoric remains, concentrated to the southwest of Pyu city. These have been the focus of 2017-2020 investigations by the Mission Archéologique Française au Myanmar (MAFM). Of particular interest was the ‘Neolithic mound’, recorded by Bob Hudson and Nyein Lwin in 2012, which the MAFM re-excavated in 2017 and the results of which are presented elsewhere. Here we report on 2018-2019 excavations at HL-TP1, a mound situated c. 850 m northeast of HL19. This location was spotted by the lead author in 2017, whilst prospecting for other ‘Neolithic’ sites, which he suspected HL-TP1 might be due to the cord-impressed pottery and topography. Subsequent work proved the lead author to be substantially wrong, but in an interesting way. The 2018 excavation of a 4x4 m testpit encountered dense occupation deposits extending 4 m deep, with a test shaft descending to 9.5 m depth, and still finding brick. Our task in 2019 was thus to reach sterile at all costs, which we tackled by extending to an 8x8 m testpit of 4m depth, then contracting to a 6x2 m testpit of 4 m depth, and finally a 3x1 m testpit, which finally hit sterile at 2.5 m depth. HL-TP1 is thus the deepest testpit ever excavated in Myanmar, for a total of 10.5 m. With a total of 28 radiocarbon determinations, HL-TP1 is also the most densely dated testpit in Myanmar. Its results are quite surprising and the interpretation is rather complex.