We evaluate the dipole decay rate inside a hollow high quality factor Q rec
tangular quantum dot activity. The cavity modes are quantised, allowing the
position-dependent spontaneous emission rate to be evaluated, leading to t
he possibilities of enhanced and inhibited decay rates. In particular, in t
he small size limit, especially when all sides of the cavity are less than
lambda (the electric dipole transition wavelength), we show that the sponta
neous emission process is possible only via a few cavity modes. The results
are illustrated with reference to sodium atoms inside a sub-micron cavity.