  We use Chandra data to infer that an X-ray bright component of gas is in the
process of separating the radio lobes of 3C 442A. This is the first radio
galaxy with convincing evidence that central gas, overpressured with respect to
the lobe plasma and not simply a static atmosphere, is having a major dynamical
effect on the radio structure. We speculate that the expansion of the gas also
re-excites electrons in the lobes of 3C 442A through compression and adiabatic
heating. Two features of 3C 442A contribute to its dynamical state. Firstly,
the radio source is no longer being powered by a detected active jet, so that
the dynamical state of the radio plasma is at the mercy of the ambient medium.
Secondly the two early-type galaxies, NGC 7236 and NGC 7237, one of which was
the original host of 3C 442A, are undergoing a merger and have already
experienced a close encounter, suggesting that the X-ray bright gas is mostly
the heated combined galaxy atmospheres. The lobes have been swept apart for
about 10^8 yrs by the pressure-driven expansion of the X-ray bright inner gas.
