Fraction of merging X-ray AGN in clusters (main sample) as a function of distance from the cluster centre. For comparison, we overlay the respective fraction for the 1914 non-AGN cluster galaxies (control sample (ii)). The hatched line represents the average value of the merging fraction derived from the sample of 1987 field X-ray AGN (control sample (i)). Error bars indicate the 1σ confidence limits for small numbers of events (Gehrels 1986). The results indicate a significant excess, at the 2σ confidence level, of merging AGN hosts in cluster outskirts.