Extract from recent announcement on capital raising...

Extract from recent announcement on capital raising (28/11/2007):

“After taking into account the firm allocations to be made to Peter J Woodford, the shortfall under the Rights Issue was 17,961,688 shares. The shortfall has been taken up by existing shareholders who applied for additional shares under the Rights Issue and the underwriters�
Can someone tell me why the underwriters got in on this action, when existing shareholders did not get all they asked for?

Should existing shareholders not have priority?