As Jarak commands the Alphans to die, his ships are suddenly attacked. The 19th June script had some unusual alien language at this point, but it was gone from the 1st July blue page version of this page.
The other major difference is that there are 6 alien ships, pursing Jarak's 4 ships. Over several scenes there is a extended space battle, as Jarak's ships destroy two of the pursuit ships, but are outmanoeuvred and one by one they are destroyed.
50
111 EXT. ALPHA. SFX. 111
There is a blinding flash, and the first of the four
spaceships is destroyed. The fragments cascade in
brilliant flames, all over Alpha, lighting up the whole
base.
112 INT. KOENIG'S OFFICE/MAIN MISSION. 112
The entire area is whited out in the flash.
RENA turns in terror to JARAK.
RENA
They've found us!
JARAK looks round. He sees that KOENIG is affected by
the blinding light and is beginning to recover.
KOENIG, staggering at first, but gaining strength, moves
towards the console.
ON JARAK
He runs down into Main Mission, talking to the spaceships
desperately. His voice has a weird, reverberating,
electronic quality.
JARAK
Vade bindi jaggar - doz!
113 EXT. ALPHA. SFX. 113
As the remains of the first spaceship cascade over
Alpha, the remaining three begin to move off.
ANOTHER ANGLE
Six more spaceships of identical design, head towards
the Moon. Suddenly they change course.
ANOTHER ANGLE
The six spaceships are in pursuit of the three.
ANOTHER ANGLE
ON the six spaceships. Three split and go high, the
other three go low.
114 INT. MAIN MISSION. 114
KOENIG reaches the console and presses a key. He
looks up at the Big Screen.
CONTINUED:
The blue version of this page on 1st July drops the alien language, but it otherwise identical. On some unknown date, scene 113 was replaced with new text (on Nick Allder's script, a piece of white paper literally cut and pasted over the scene)
Scene 113
EXT. ALPHA. S.FX.
As the remains of the first spaceship cascade over Alpha, the
remaining three begin to move off.
ANOTHER ANGLE
An enormous Battle Cruiser heads towards the Moon.
ANOTHER ANGLE
Galactic Battle Cruiser is now in pursuit of the three.
So why did six alien ships become one "Galactic Battle Cruiser"? One problem that was that, with just two alien ship models, it would take a lot of time to film all the multiple exposure shots to build up the 10 ships required. They was space battle earlier in the episode between three Eagles and 3 alien ships, and similar shots could be repetitive.
Another problem was that the alien ships were all identical. It was impossible to tell which side the ships were. In the end, the four surviving ships would assemble over Alpha, just as Jarak's ships had earlier in the episode, making the climax ambiguous.
Fortunately, the special effects team had just discovered a solution. The alien ships had been built by a new external model maker, Martin Bower. When Bower had been interviewed, he had shown them an old model he had built as a teenager. Brian Johnson offered to buy this model, with a few updates, to become the Battle Cruiser that attacks Jarak's ships. The difference between the two sides was obvious. The new model looked much bigger and more powerful than Jarak's ship (although it was actually a slightly smaller model).
Here are the rest of the space battle scenes, which play out as Jarak flees to Medical, pursued by Koenig.
121 EXT. SPACE SFX 121
The three groups of spaceships converge. JARAK's three
ships fire first, shooting out green rays from either
side as they bank steeply to give them shots at the
ships both above and below them.
One of the three is hit from rays from both sides
simultaneously. It explodes in blinding white light
and particles fly out into space.
The two survivors change course rapidly and fly up
through the formation of three which are bearing down
on them.
The five attackers now re-form and pursue.
Scene 121
EXT. SPACE. SFX.
JARAK's three ships fire first, shooting out green rays from
either side as they bank steeply to give them shots at the
ship. The shots have no effect.
One of the three is hit by rays from the Battle Cruiser, it
explodes in blinding white light and particles fly out into space.
The two survivors change course rapidly.
The battle cruiser moves off in pursuit.
125 EXT. SPACE SFX 125
The five pursuing spaceships have now surrounded the
two survivors. They close in from five directions.
Again the two fire first. Green rays shoot out and
score direct hits on one of the pursuers. It explodes,
leaving a blinding flash behind it. One of the two
spaceships rockets up in the frame, while the other
goes down. Two of the surviving attackers follow
each.
Green rays shoot out from the two who pursue the
lower ship. It is hit twice and explodes, leaving only
one survivor.
All four attackers turn towards it.
Scene 125
EXT. SPACE. SFX.
The Battle Cruiser bears down on the two survivors. Again the two
fire first. Green rays shoot out and score direct hits on the
battle cruiser leaving a blinding flash behind it. The two
spaceships rocket up in the frame, the battle cruiser follows.
A green ray shoots out from the Battle Cruiser towards the two
survivors. One ship is hit and explodes leaving only one
survivor.
The Cruiser turns towards it.
129 EXT. SPACE. SFX.
Four spaceships converge on the one surviving JARAK
ship. They swoop in from above and below, and from
either side. They all fire simultaneously and the
ship is hit by four green rays. It explodes instantly.
Scene 129
EXT. SPACE. SFX.
The Battle Cruiser converges on the one surviving JARAK ship. It
fires and the JARAK ship vapourises.
132 EXT. ALPHA. S.FX. 132
Four spaceships swoop down towards Alpha.
The Battle Cruiser swoops over Alpha and hovers.