After the homeworld of the Spaeron shoal, Oceanus Pacifika, was destroyed by Daleks, the Spaeron negotiated a treaty with Earth, the Aquarius Condition, which allowed the Spaeron to live in Earth's oceans. However, the Spaeron betrayed their humanity by melting the polar ice caps, flooding the entire planet. The Spaeron Shoal based themselves in the House of Commons in the newly-submerged London.
The Galactic Council sent a team led by Harris to wipe out the Spaeron for flooding Earth. The Tenth Doctor and Heather McCrimmon came to London at the same time as Harris' crew and were able to find peace between the two groups. The Doctor took the Spaeron to Kerun Za, a new planet where they would be able to live without bothering another species. (COMIC: The Aquarius Condition)