High-Voltage CMOS (HV-CMOS) sensors are emerging as a prime candidate for future tracking applications that have extreme requirements on material budget, pixel granularity, time resolution and radiation tolerance. This article presents a new HV-CMOS prototype chip, UKRI-MPW0, aimed at pushing some of the boundaries of these sensors. This HV-CMOS chip implements a novel sensor cross-section which is optimised for backside biasing to unprecedented high voltages. Preliminary measurements have shown the chip is able to withstand high bias voltages (>600V) much beyond the state of the art, thus promising a large improvement in radiation tolerance. The design details and initial performance evaluation are presented in this paper.