Ashley Pharoah and Matthew Graham, who were also behind the predecessor Life On Mars, said they compromised on some of their ideas for the first series.
Speaking at a BBC question and answer event for aspiring writers, the pair said Ashes was commissioned quickly by BBC One after the success of Mars.
Graham said: "Then we started talking about what we call our three year plan, which is if, all things being equal, we can run Ashes To Ashes – if we have a series two – if we can run it beyond series two to series three, as is our hope, we can actually unveil a bigger mystery, a bigger plan. And ultimately reveal a lot more about the characters.
"The first series of Ashes To Ashes was more about laying the ground rules again, and just kind of having fun and getting people into the ’81 groove. And then we’ll start playing out the bigger mysteries... Now we can start darkening it, now we can start doing some of the things we did in Mars. We’re bringing in bigger mysteries and more textured stuff, I think. We weren’t sure about doing it in this initially."
Pharoah added: "One of the things we talk about in series two of Ashes is how much more muscular the early Eighties cops would be – obviously I can’t give too much away. But you can tell we’re excited by series two."
The paid spoke at length about their writing, as recorded on a Manchester Evening News blog, with topics including the importance of Gene Hunt to the shows.
Graham said: "Philip Glenister brought such amazing magnetism to it, that right from the first couple of days’ filming, we thought, ‘Oh bloody hell, this guy’s really good and this character could really catch fire. So let’s make sure we feed that character as much as we feed Sam.’"
> Read Digital Spy's review of Ashes series one