Figure: Flow diagram of randomisation, follow-up and principal analyses

* Details of how age is defined are given in Annex 3. The batch could also include trial participants invited 3 years ago at ages 71-73 (but now aged 74-76) for a second invitation and those invited 3years ago at ages 74-76 (but now aged 77-79) for a third invitation.

†Exclude from the primary and main subsidiary outcome analyses: duplicate randomisations; NHS records could not be flagged; withdrawn from BSP; already dead or moved from screening clinic’s catchment area; or objective prior record of cancer, breast disease, or breast surgery.

† Exclude from the primary and main subsidiary analyses women for whom, from objective prior records, the randomised trial allocation is unlikely to affect whether or not they attend for screening (eg those who had not taken up their previous screening invitation) – see text.