Esther McStay - why has the Wirral West MP missed out on promotion, again?

So the big promotion never came, again.

As Nicky Morgan and Liz Truss made the well-trodden walk passed the flashing bulbs into Number 10 and into Cabinet positions, Esther McVey's journey was not so fruitful.

The Wirral West MP remains in the Department for Work and Pensions as Minister for Employment, and will now attend cabinet meetings. That does not, however, make her the Cabinet Minister she was widely tipped to become.

It comes three months after she was overlooked for promotion to Secretary of State for Culture, Media and Sport, with Sajid Javid instead replacing the outgoing Maria Miller.

Why? There are a number of theories.

One is that others have simply impressed more.

Loughborough MP Nicky Morgan, who replaces Michael Gove at Education, has earned praise for her performances at the Despatch Box in her role in the Treasury and as Women's Minister. Liz Truss, the new Environment Secretary, is viewed within some Tory circles as a potential leader of the party: intelligent, hard working and extremely ambitious.

But another theory focuses on trust.

Nicky Morgan has earned it at Number 10, towing the party line on all-women shortlists; Liz Truss is well-liked by David Cameron (he personally intervened when her local party tried to de-select her in 2010) and has been rewarded for her attempts to reform childcare which were blocked by the Liberal Democrats; Matt Hancock, also promoted today, is a loyal member of the Osborne camp, as is Sajid Javid.

Can the same loyalty and trust be attributed to Esther McVey? One incident is cited time and time again.

When former DCMS Secretary Maria Miller apologised to Parliament and was asked to pay back £5,800 of her over claimed expenses, Esther McVey looked to condemn her colleague on ITV's The Agenda.

"I can honestly say it wouldn't be how I would have made an apology. But different people have different styles and do things in different ways."

Asked if Mrs Miller should keep her job, she said: "David Cameron has the final say on this. He's standing by her."

WATCH: Esther McVey on Maria Miller's apology

It didn't go down well at Number 10, with some close to the Prime Minister criticising her comments. Some believe it cost her promotion back in April. Today's reshuffle suggests those wounds may not yet have healed.

Others though point to the fact Miss McVey has already moved quickly up the ministerial ladder since her election in 2010. Attending cabinet meetings too is a boost, and perhaps reward for her performance at the DWP in pushing through, and publicly defending, the government's welfare reforms.

There is little doubt her attendance at cabinet will help her profile and enhance her reputation, yet does that leave David Cameron open to criticism?

His desire to promote women into the higher echelons of government is no secret. Esther McVey is not just a woman, she's a northern, working class woman, who 'looks good on TV'.

Yet by denying her a top, departmental brief, and instead offering more exposure in the build up to a General Election, the Prime Minister could be vulnerable to accusations of tokenism.