make installworld - permission denied

[Mark]

Urgh, it was all going so well. I suppose it had to happen:

I did as the hallowed handbook commanded:

#make buildworld
#make buildkernel KERNCONF=L004
#make installkernel

I rebooted into single user mode:

#mount -a
#cd /usr/src
#mergemaster -p
#make installworld
(setting of variables omitted, i'm typing from the screen!)
/tmp/install.XXXXXXXX make -f Makefile.inc1 reinstall
make: Permission denied

***Error code 126
Stop in /usr/src

***Error code 1
Stop in /usr/src

Any ideas? AFAIK my permissions are still at their defaults.

Apologies for any major errors I may have unwittingly made,
this is my first buildworld. Please tell me my setup is NOT
ruined, it still had that two-week-old-fresh-install feel to
it and I had everything just how I like it.

Putting on a brave face.