It may not have been too enamoured with the prospect of running Renault-derived V6s this season, but Red Bull Racing admits that there would have been more work to do had it managed to change engine suppliers after a dire 2015 campaign.

The fall-out between RBR and Renault was very public and, for some time, could have led to the four-time world champion constructor withdrawing from the sport, as it appeared that the rift with Viry-Chatillon was too big to bridge after alternative suppliers - namely Ferrari and Mercedes - made no secret of the fact that they were unwilling to partner RBR on the team's terms.

With some sort of healing process put in place towards the end of last year, however, RBR will be on the grid, running Renault power units under the TAG-Heuer moniker and with Mario Ilien providing the tweaks the team hopes will move it closer to the pace and improved reliability. It may not have been the preferred option - although year-old Ferrari engines was hardly a desired alternative - but the design team in Milton Keynes admits that retaining a familiar power unit made the build-up to 2016 a lot smoother.

"We were looking at other power units, there is no secret to that," chief engineering officer Rob Marshall confirmed, "We had a good idea of what requirements those would have on [the RB12] car design, so we were looking at various different car design concepts in parallel.

"It is obviously never easy when you get a late decision on what engine you are going to put in but, in hindsight, keeping one which is generically similar to one we took out did simplify the task. Whilst we could have squeezed a different engine on a tighter timescale, it made it much easier to have one that was the same shape and architecture.

"If we were going to put a different power unit in, the car would be quite different architecturally, basically because the various different power units up and down the grid need different installations - where the batteries are, how big they are, that sort of stuff. It would affect the overall car architecture and also the cooling requirements for the power units are different but, by staying with the same unit, we understood all the heat rejection requirements so, while it was late, it meant we could be quite confident we could get it right."

With the change in the terms of Renault's supply deal, there will be less technical collaboration between the two parties, but Marshall admits that the French connection will still be keeping an eye on how the RBR package runs this year.

"I think Renault are still interested in how the whole power unit/chassis should be integrated, but I guess we want to see how we move forward from here," he noted.

Although the matter is not open for debate, there will always be the question of whether remaining with Renault was the right option for Red Bull, but chief technical officer Adrian Newey is convinced the team took the best option available.

"Firstly, the option was closed to us with regard to the one year out of date Ferrari," he clarified, "Secondly, you are dooming yourself to always be some way behind and, while I believe I am not allowed to refer to who makes the power unit these days, our power unit manufacturer are on a good course now. They had a good winter. Obviously, it is a big deficit to make up, but I think, with the new procedures, the new budget, the way they are working, they are on a good path, so I am confident they will slowly close the gap."