[OT] Bonehead DNS question

[walt]

I'm having a DNS problem which is a combination of a recurrent
flaky nameserver at BBC and my own local caching nameserver
(which I suspect may be mis-configured).

Their 'primary' nameserver (ns1.bbc.co.uk) has been intermittent
for several months now, so I often can't resolve 'www.bbc.co.uk'.

My puzzle is why my own nameserver won't fall back to using BBC's
secondary servers (of which there are many).

Using a packet sniffer, I can see that my server fetches the
names of at least four backup servers at BBC -- but then my
server insists on resolving those names by using the primary
server which is *down*, and so the whole effort fails.

This scenario just seems too stupid to be true -- what good
does it do anyone to have secondary name servers if they can't
be found?  Is my own nameserver just being stupidly configured,
perhaps?

Any clues much appreciated!