This paper presents the latest design, development, and field trial results of a comprehensive ultra-broadband terahertz (THz) prototype platform, for the next-generation integrated sensing and communication (ISAC) applications. Particularly, the hardware architecture, link budget, and the baseband are firstly introduced. Then, representative scenarios are carefully selected, and the corresponding field trials are conducted extensively to verify a number of the most concerning parameters. According to the analysis of the results, it can be observed that this work has realised a co-hardware and co-waveform ISAC prototype, which supports high data rate communication and millimetre-level high resolution sensing functionalities. The prototype has also adopted THz compound semiconductor device, digital-to-analogue and analogue-to-digital converter boards, and low complexity signal processing techniques to simultaneously provide up to 3.5 km long-distance, up to 240 Gbps high data rate, and 17+ bit/s/Hz high spectrum efficiency ISAC service.