RUN fsck MANUALLY

Hi,
I've been ruing Ubuntu for a few weeks on an old-ish laptop (I've used it before on other computers), and trying to log on just now, it's telling me:

/dev/sda1: UNEXPEXTED INCONSISTENCY; RUN fsck MANUALLY.
(i.e., without -a or -p options)
fsck exited with status code 4
The root filesystem on /dev/sdal requires a manual fsck

It's then started something called:
BusyBox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built-in shell (ash)

And my command line begins with:
(initramfs)

Any help with what to do from here would be greatly appreciated

p.s.
I've turned on & off again few times, including starting in recovery mode - same result.
I've also already run Ubuntu from disk to get my files copied onto a pen drive.