Re: Time to claw some back
I left ICL in 2001 - they had already at that point switched their internet link from a fully routed (but firewalled as approriate) internal network (220.127.116.11/16) to some seperate proxy / gateway in another net range run by ICLNET. 18.104.22.168 has basically been dead to the world since then, but is still allocated to (now) Fujitsu.
Sure, the renumbering of internal machines to the new 'private lan' scheme was taking ages, and most stuff still used 22.214.171.124/16 when I left, but it doesn't matter - the only internet access they have is through application-level proxies so they'll never need to route to a "real" 126.96.36.199/16 address if it was relinquished.
Same goes for most others - there is no need for them to all renumber before giving up a netblock.