By fiat. Linked article includes photo of three women in Dalek costumes beating up an inflatable TARDIS for no discernible reason.
-- Bob
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Then the horns kicked in...
...and my shoes began to squeak.
...given an average run of three seasons per Doctor, that would mean the BBC would have to re-retcon the regeneration limit sometime in the 22nd Century.
Yes, I am that nerdy.
Mr. Fnord
interdimensional man of mystery
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"I. Drink. Your. NERDRAGE!"
Personally, I was always under the impression that the regen limit was statutory, not biological, based on things said here and there in the series, most noteworthy being the one time the council of the time lords offered the Master new regenerations if he did something for them. The twelve limit may well have been simply a population control measure -- and since there is no longer a population needing control, there is no need for a limit any more.
-- Bob
---------
Then the horns kicked in...
...and my shoes began to squeak.