Williams deputy team principal Claire Williams admits the team felt "embarrassed" to have been forced to delay the arrival of its 2019 auto to Barcelona.
It cancelled a planned filming day last weekend due to the late completion of the auto and that delay spilled over to this week, with its FW42 being delivered to the Circuit de Catalunya paddock early on Wednesday morning. "It's not a situation we ever wanted to find ourselves in", said Williams, speaking to media at the test, as quoted by Motorsport.com.
Debutant Russell was 13th fastest. "It appears that they have a better package than they had past year".
Following a morning of set up work, George Russell was finally able to make it out on to track to complete the first installation lap.
"Particularly for a team like ours that has managed to deliver a race auto to testing for the past 40-odd years".
Kubica, who has handed the vehicle over to team mate George Russell for the rest of the day, said he hasn't been able to do any preparation for the first race of the season yet.
She ruled out cash-flow as a problem.
Media speculation has focused on the future of technical director Paddy Lowe, who joined from champions Mercedes in 2017 with responsibility for overseeing design and production of the new vehicle.
The team cancelled a media briefing that had been scheduled for Lowe, saying it would now not take place until next week's second test after the vehicle had undertaken significant running.
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When asked if she was satisfied with Lowe's performance, Williams replied: "I've read a lot of speculation about his position".
"That was refreshing for me and made me quite proud of the guys at how hard they're working".
Russell was due to drive on Wednesday morning before handing over to Kubica.
Lowe, who presided over a nightmarish 2018 campaign in which Williams finished bottom of the constructors' standings, has now failed even to deliver a vehicle to the start line on time.
I think there's still something to put on the vehicle, probably not a lot", he continued, "but for sure there are things that were compromised.
"Clearly we're doing everything we can to condense the programme that we had, to make sure that we maximised the time available and we really focused our efforts and attention on the most important and critical areas to make sure the auto is in the best shape possible for Australia".
Russell completed only 23 laps on Wednesday. "Ferrari are very, very strong right now, they are racking up great mileage as well", he said.
"Of course as the boss it's my ultimate responsibility, but it's everyone's responsibility in any team to make sure they play their part in getting whatever your product is to the place that it needs to be".