How are these people affected?

Under Serps these people often had poor National Insurance records so they qualified for little or no Serps pension on retirement. To make matters worse they often missed out on the full basic state pension as well (you can get more information on the basic pension by looking at www.statepension.co.uk). Under the S2P system people who earn less than a minimum level set by the Government will be treated as if they did earn this minimum for S2P purposes. So their pension entitlement on retirement should be higher.