Professor Alice Sullivan, the study’s lead author, said the findings may show that the "old boys network" was still helping men to achieve more.

“I think it’s a definite possibility because male private schools have a strong tradition of getting pupils into top jobs, particularly in areas like banking which are very highly paid and which male dominated in general.

“Women’s private schools, particularly in the 1980s, when these people would have been attending, tended to have a less academic focus and were less ambitious.

“Single sex schools for girls often had a different goals so women were not encouraged be in the same position in the jobs market as men.”

She said there was a danger that the children of parents who could not afford a private education risked never achieving their full potential.

“Parents with the necessary means are increasingly investing heavily in their children’s education, and the danger is that less advantaged children are left behind,” she added.

The researchers also found that gaining a university degree helped in securing a top managerial or professional position, such as a chief executive, doctor or lawyer, by age 42.