Well I tried the tutorial, and I found a few interesting things.

1. With the N3 set tp 90%-92%, and pressing the IAS button at V₂+10, the L-1011's VS went into the brown (descending), not the blue (climbing)! I had to push the throttles to the max to start climbing.

2. After passing through 10,000ft, and starting the climb to FL370, using the IAS set at 300 Knots, and a climb power of N3 87%, again the L-1011's VS went into the brown (descending), not the blue (climbing)! This time, I went I used the A/T set at 300 knots, and set the VS to 1800 (in the blue), but the speed sat at about 285, and by the time I reached cruise altitude, FL370, the speed was 257 knots, and using the A/T didn't change a thing. At cruise altitude, I turned the A/T off, then on again, and the L-1011 slowly increased to 300 knots, but I had to reduce it to 279 knots to maintain Mach 0.84.

Another weird thing was that using "Ctrl+Shift+G to arm the Takeoff mode of the Flight Director", when the L-1011 reached 60 knots on the takeoff run, the Alpha Mode Flag came up in the IAS Display, and it made it very difficult to do a proper takoff as described in the tutorial.

I never had any problems with the tracking of the route at any stage after switching it to HDG, FMS, and turning NAV Mode OFF. It tracked the route just like it should.

I also tried this by entering the POS two ways. The first way was as described in the tutorial:

2(N) 5 1 2 8 1 INSERT 4(W) 0 2 7 8 INSERT

and the second way was the way I would normally do it for EGLL Gate 317:

2(N) 5 1 2 8 1 INSERT 4(W) 2 7 8 INSERT

and it made no difference to the way the L-1011 followed the route, so both worked exactly the same (so I see no reason to add the 0 into it, because as you add the other numbers into it, they fill the correct places without it (but it could be the way that Tom Beckett was taught to enter them)).

I can only think that you are either doing something wrong with entering the coordinates at EGLL Gate 317, or something is not set correctly on the AP, so it isn't following the route - like you are leaving the NAV Mode Switch ON, and/or the AP is tracking something else when you switch the NAV Source Selector Switch to FMS. I'm at a loss as to why it won't track the route like it should.