Ratio of expected to observed ionising photon flux Q(H⁰) for the regions labelled in Fig. 8, versus the age of the oldest cluster in each region (best-value estimate obtained from the median of the age PDF; masking cluster with ages > 10 Myr). For region 5, which is hosting exclusively O stars, we assume an upper limit of 3 Myr for the age. The dashed horizontal line indicates an f_esc = 0. Left panel: points are colour-coded according to the median E(B − V) in each region (Balmer decrement estimate). Right panel: regions are colour-coded according to their total GMC mass. Empty black circles indicate regions hosting no GMCs.