In this paper we present the first scaling results from Isambard, the first production supercomputer to be based on Arm CPUs that have been optimised specifically for HPC. Isambard is a Cray XC50 `Scout' system, combining Marvell ThunderX2 Arm-based CPUs with Cray’s Aries interconnect. The full Isambard system was delivered in late 2018 and contains a full cabinet of 168 dual socket nodes, for a total of 10,752 heavyweight Arm cores. In this work, we build on the single node results we presented at CUG 2018, and present scaling results for the full system. We compare Isambard’s scaling results with Aries-based XC systems based on x86 CPUs, including Intel Skylake and Broadwell. We focus on a range of applications and mini-apps important to the UK national HPC service, ARCHER, and to Isambard project partners.