I remembered reading an article about the Häkkinen & Williams negotiations a few years ago, so I did a bit of searching and found it: http://atlasf1.autos...bra/graham.html
"Mika got his first chance to drive in F1 through Lotus but it soon became clear that Peter Collins was putting his money on Johnny Herbert, and in a small team that meant Mika would possibly be left out in the cold. According to Keke Rosberg, the situation at Lotus had reached a point where it was time for the Finn to make a career change if he was to advance in F1. Once the rumours began that Mika would be going to Williams, Lotus began a concerted effort to negate Mika's worth by pointing out his weaknesses to other teams. Later Collins admitted to Rosberg that this was merely a negotiating tactic as he tried to retain Mika at Lotus, not his true opinion of Hakkinen. Collins then claimed Hakkinen already had a contract with Lotus, although later it was ruled that rather than a contract, there was in effect an agreement that an agreement would be made. Everything was looking promising with the contract for Williams ready to be ratified and Mika set to drive alongside Alain Prost.
Then the bombshell dropped. Williams was late in registering the team's entry for the 1993 season, and was about to be left out of the running. The only way for Williams to be permitted to participate was by special agreement, which needed the consent of every team in the competition. Peter Collins, seeing a golden opportunity, refused his consent if Williams persisted in signing Hakkinen. Frank Williams was prepared to negotiate for the Finn but Collins announced that Mika was not for sale. Willams cancelled the contract. "