The Grove-based outfit is understood to have entered into a seven-year deal with Mercedes, and the move is playing dividends already after its impressive showing during pre-season testing and the Australian Grand Prix.
Williams emerged as the closest challenger to Mercedes on pace in Melbourne and, had it not been for Felipe Massa's first-lap elimination and Valtteri Bottas collision with the Turn 10 wall, a podium finish would have been likely.
These positive signs for the season ahead have been largely attributed to the decision to swap from Renault to the potent Mercedes engines last year, something Williams suggests was due to careful consideration.
"We were in our second year with Renault and we had a long history with them," she explained.
"But the regulation changes were as they were and we had to do a huge amount of diligence to see where Renault and the other engine manufacturers were going to be.
"It was obvious early last year as to where some of them were in their development stages, so we spoke to both Renault and Mercedes about it and we took the decision to go with Mercedes.
"It was a really conscious decision."
Williams also revealed that Mercedes motorsport chief Toto Wolff also played a part in the decision.
"We had the benefit of him being at Mercedes and, as he is still a shareholder at Williams, we were able to exchange information with him."
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