Explore a rare-event study on a simulated power system where grid-scale batteries provide regulation and emergency frequency control ancillary services. Delve into the use of the skipping sampler, a Markov Chain Monte Carlo algorithm for rare-event sampling, to construct conditional distributions of power disturbances leading to frequency excursions outside the normal operating band and load shedding. Examine the potential saturation in benefits and competition between the two services as the battery maximum power output increases. This one-hour lecture by Maldon Goodridge at the Alan Turing Institute offers valuable insights into the complexities of frequency regulation and contingency services in modern power systems.