He focuses his research on the study of nuclei at high angular momentum, with a special interest in nuclear isomers (excited, metastable states of nuclei). In 2019, he received the Ernest Rutherford Medal and Prize from the Institute of Physics, for his work on nuclear isomers.

Nuclear isomers are discussed in, for example, "Energy Traps in Atomic Nuclei", by Philip Walker and George Dracoulis, Nature 399, 35 (1999); "Review of metastable states in heavy nuclei", by G.D. Dracoulis, P.M. Walker and F.G. Kondev, Rep. Prog. Phys. 79, 076301 (2016); and "100 years of nuclear isomers - then and now", by Philip Walker and Zsolt Podolyak, Physica Scripta, 95, 044004 (2020).