My understanding is that some shareholders who were eligible did...

My understanding is that some shareholders who were eligible did not take up their entitlement. These unclaimed shares were then distributed amongst all those who were entitled and who applied for additional shares (and paid the 5c).

Another group are the ineligible shareholders (probably mainly international). These shares were taken up by RBS (who paid AHX the 5c) and who are obliged to sell them and to pass on to the ineligible shareholders any gain above 5c (less costs).

I also think some of the selling seen in the last couple of days may be RBS unloading these shares.