- "It's payback time. Give 'em what we owe with extra interest."
- ― Burford
This variant of the mission is automatically played in single-player, but can be optionally selected in multiplayer. The 12B variant is only available through multiplayer.
Burford: The Valahia have launched their attack on London. Allied forces are already engaged with them. They've deployed the same Spiridus we saw over Tokyo airspace, meaning London is in serious danger. So far they haven't revealed any new weaponry other than what we saw in Tokyo, but stay sharp. Analysis of data suggests the Spiridus lacks mobility due to its massive size. Use a high speed aircraft for hit-and-run tactics. Or a high spec one for close range attacks. It won't get away from us this time! Antares Squadron, destroy the aerial base Spiridus. This battle will settle everything. You are ordered to come back alive and victorious!
The Spiridus will be flying over London and preparing to attack. The player must destroy its three anti-ground electrolaser cannons - one on each end of the Spiridus, and one in the back. They will only be vulnerable when charging up for an attack. Periodic jamming will also occur, temporarily preventing lock-on and disabling radar.
There will also be two Su-27s protecting the Spiridus, as well as four AA guns on the Spiridus itself. The AA guns will constantly respawn when all four are destroyed; destroying only three of them and keeping one alive will prevent the other three from respawning.
When all three electrolaser cannons are destroyed, a fourth one will appear, this time as an aerial weapon. The player must avoid the laser for the remainder of the mission by flying very fast or staying below the Spiridus.
Multiple AA guns, flak guns, and SAMs will appear on the Spiridus. Fire control units (labeled as "FCU") will appear as well, and the player must destroy these to lower the Spiridus's power. After the player destroys two waves of FCUs, the anti-air electrolaser cannon becomes vulnerable. Destroying the laser cannon will destroy the Spiridus and complete the mission.
Earning an S rank on Nightwatch does not require completion within a certain time or score range. Instead, the S rank requires minimal damage to London. The MPG must be at 90% or above upon completion of the initial stage.
- Gunboat Offside - appears in the River Thames, underneath the Tower Bridge, after two Su-27s have been shot down.
Burford: Spiridus has been destroyed. Well done, Antares Squadron. London has taken a lot of damage but the worst case scenario was avoided and that's what matters. Hopefully this will put Valahia back in their place... but we're at a loss as to what they want. The Valahia's motives are still unclear. They targeted Tokyo and London, two hubs of economic and financial power, with high spec weaponry. They operate on too large a scale to be terrorists. They obviously have firm financial backing. Oh, uh... This isn't something I should be discussing right after you finished an operation. Thank you for your efforts in protecting London. You deserve a good rest, Antares Squadron.