The first Labour government lasted only nine months. Parliament was dissolved on 9 October 1924; five days later Macnamara was formally adopted as Liberal candidate for North West Camberwell at a constituency association meeting in the Surrey Masonic Hall. It was twenty-four years since he had first been elected to Parliament. Throughout all those long years, he reminded his supporters, Camberwell folk had supported him with unbroken loyalty – loyalty for which he could never sufficiently express his gratitude:

In October 1900, after his first campaign, the South London Observer (and) Camberwell and Peckham Times, the local Conservative newspaper, received Macnamara's 1,335 vote victory with resignation as an admittedly brilliant conquest of an unstable seat: