Super. The deep end of things is not so bad with all the folks here willing to help.

Success at last! 
Many thanks to those who offered suggestions.  As it turns out, the motor I am disassembling DOES have a mechanical fuel pump which engages the camshaft.  Once I removed that, the camshaft slid out quite easily.
In my (admittedly) limited experience...should I say, minor experience, yuk, yuk...the cars I have worked on have all had electric fuel pumps, so I was not expecting a mechanical one.  In fact, the two manuals I have both say the fuel pumps on all Morris Minors are electric, with no reference to mechanical fuel pumps or how to service them, although one book does show a diagram with a mechanical one which I obviously overlooked.
So, thanks to Doug L and Willie B for your help with this.  I only signed up for the Forum a few days ago, and already you guys have provided some valuable assistance! 
Many thanks.
Mike in Oklahoma

There is a key... but it's the one where the timing pulley mounts so it is at a much smaller diameter than the journals on the cam.  It won't prevent removing the cam.

Your post says have taken all the obvious stuff off with the exception of possibly there being a mechanical fuel pump.  If it is mechanical, remove it from the back of the block.  

My second question is... have you removed the triangular cam retaining plate from the front of the engine?  If you remove the pulley and leave the plate, you can have a lot of axial travel on the cam and you won't be able to remove it.

Hmm, good question.  I'm pretty sure it is an electric fuel pump.  The motor I am working on is a spare that I bought out of a scrap car.  The one I am rebuilding is the original motor, and it definitely has an electric fuel pump.  
I have removed the tappet covers and can see the cam shaft moving around inside, I just haven't been able to get it out!

Does anyone know if there is a key that must be removed, like a woodruff key, or something else?

Is the fuel pump driven off the cam?

Yes, the pushrods and lifters are out.  The oil pump, crankshaft, crank pulley and pistons are still on.  I have removed the distributor and distributor drive, the cam gear and chain and the camshaft mounting plate.  When I pull on the camshaft it seems like it is blocked by something inside the block.  It rotates freely and moves forward and backwards a tad, it just won't come out.  Wondering if there is still something else I have to do in order to extract it.  I've also tried pushing down on the exposed threaded end slightly, so as to free it up, but that doesn't work, either.

Have you removed the pushrods and lifters?

I'm having trouble removing the camshaft from my 948 Morris.  I can move it forwards about 1/2", but it won't come out all the way.
Any suggestions?
Also, my manual says to remove the Woodruff key, which I have not done, which may be the problem.  How is this done?
Thanks!