The amount of donor sperm supplied by Denmark to the UK – and to many other countries – has rocketed in recent years. Kate Brian, who has reported on fertility issues for two decades, travels to Copenhagen to meet some of the 250 men who regularly donate at European Sperm Bank, receiving around £30 per visit. How rigorous is the selection process for becoming a donor? Is the incentive merely financial? And how do the men feel about producing potentially hundreds of children, many of which may contact them in years to come?