, the average (mean) hourly rate of its female members of staff is 33.7% lower than men, a disparity that's worse than the UK's average rate of 18.4%.
In their report they attributed their gap to, "a clear gender imbalance in our very senior roles at the top of our salary grades". At Norwich-based media group Archant, which had a median pay gap of 6.4%, women earned 8.5% more than men in bonuses, and at sports vehicle manufacturer Ransomes Jacobsen in Ipswich the median pay gap put women's pay 7% higher than men's.
UEL senior lecturer Elaine Yerby welcomed pay reporting, but said more needs to be done to break down stereotypes around jobs: "The big question is about why work associated with women tends to be paid less. The former is rightly protected by law, the latter is a variety of calculations that are more or less meaningful depending on the extent to which they compare like-for-like circumstances".
She said: "When you have a child you have to come out of the workplace".
Companies who haven't yet revealed the data were sent a final warning and not doing so till the deadline would be considered as breaking the law.
Of the around 9,000 firms with more than 250 staff required to report by midnight, the BBC notes 8,870 had done so as of 7.00am.
The government hopes that "naming and shaming" companies with large pay gaps will force them to take steps to tackle inequality.
How is the pay gap calculated? This matches the mean national pay gap pay, and is only 1 per cent better than the median national pay gap. There are also more men in leadership positions, which pay more.
For the first time, she said, every larger firm would know the average pay difference between men and women in their company.
Chief executive Susan Whelan said: "The club has made significant progress in the employment of women in recent years and remains committed to increasing both opportunities for, and the representation of, women at all levels of the business in the future". The bonus gap was 30.4% (median) and 49.2% (mean).
In March, Minister for Women and Equalities Amber Rudd, announced a £1.5 million fund to support people back into work after time out caring.
It also said it would "review how we attract more women into roles such as national clinical directors which are now mostly male".