According to the Office For National Statistics, the age at which British women marry for the first time has been climbing. Most interestingly, the number getting married for the first time in their late 30s and 40s has almost doubled in the past decade.

How can this be? Expert opinion varies:

Jo Dale is a Relationship coach who founded the Dear Mrs Herbert website, which aims to help 'smart, professional women get confident and find love', Jo is of the opinion that many professional women 'wake up' in their mid-30s only to realise they've forgotten to nurture their personal life.

Jo says: 'These women don't deliberately put marriage and children on the back-burner when they start their working lives, it just happens. An exciting career can be all-absorbing and the years just fly by.'

Psychologist Mairead Molloy, believes many women stay single for longer these days because they have unrealistic expectations about relationships.

We've become a society of perfectionists. In the past we were happy to fall in love, get married and then do our best with that relationship, for better or for worse.

Mairead adds: 'These days, women will complain that they can't meet anyone then tell me in the next breath that a man has to be the right height, have the right hair colour, the right job, the right car, almost the right DNA before he can even be considered for a date.'

Andy Maccabe, director of Loveandfriends.com, the top uk dating site which specialises in 'Thinking People' more concurs with the analysis of Jo than with that of Maireed. 'I don't think these women are being 'Unreasonable' so much as a bit unrealistic although subtle, there is a whole world of difference between the two. 

Let's take an hypothetical Loveandfriends member who we'll call Susan. Susan's an attractive, university educated, 33 year old in a good job. If we boiled down her requirements she would probably agree it amounts to an attractive man with an agreeable personality, decent job and similar backround. This sounds pretty reasonable. 

The snag is what and who Susan considers to be 'Attractive enough'. As far as she is concerned - the guys she would be interested in are in are a similar-ish level of attractiveness to her.

The reality is that we've said Susan is 'Attractive'. This is no lie, we would not call her unattractive. However, in reality she's no more attractive than many of our other members. If we were to be statistically precise and divide members into three camps of average, above average and below average looks according to who gets the most men clicking on their photos she'd be in the middle camp average. In fact Susan's the average of the average our hypothetical average looking member. 

What we can see from our site statistics is that even the average looking Susans are actually often looking more towards the 'Cream' of our men than the average looking Joe. Not the Cr'me de la Cr'me but somewhere north of 'Just a little bit above average'. These thirty something and older 'Just a little bit above average' guys get lots of attention from lots of other women far more than Susan perhaps realises. 

Susan can spend years and years waiting for an 'Attractive enough' guy who is also 'Marriage material'. Along the way she may have some dalliances with 'Attractive enough' guys who are more after something short-term or who turn out to be lacking in the job or personality stakes. During this period, unlike her grandmother would have been, Susan isn't really enthusiastic about approaches from the decent enough but less attractive guys. Susan still has the expectation of finding and marrying 'The One' who of course combines attractiveness along with the job and personality. 

Susan's friends and family tell her how wonderful and attractive she is which reinforces her reasonableness in her own mind of 'Holding out' for 'The One'. Ditto any relationships and flirtations she's had with attractive guys in the past they're taken as proof positive that she's being reasonable. 

There is no longer a large societal pressure on women to be married before they are 25 or 30's or even at all. In our grandparents day the pressure to get married meant many Susans of a couple generations ago would willingly pair up with someone who wasn't necessarily quite so attractive much sooner. 

These days there is a distinct lack of bony fingered maiden aunts and plain spoken grandmothers poking Susan in the back and telling her to 'Get a move on' and trying to match her up with decent-though-not-quite-so-sexy Duncan. 

Now-a-days many Susans refuse to 'Settle for less' and in fact see the word 'Settle' as a dirty word and defeatist ' the end to their hopes and dreams - and so they postpone even thinking about changing their mindset until later and later.'

That lack of pressure to get married, Jo Dale agrees, also contributes to women leaving marriage until later.

'Not that long ago, a woman risked being labelled a spinster ' pitied, even' if she was still single at 30. It was a scandal to have a child outside marriage. But, quite rightly, that simply isn't the case now.'

Relationship psychologist Mairead Molloy says the creeping realisation that we're not getting any younger can help to push some apparently dyed-in-the-wool singletons to settle down. She also believes the current economic troubles may also be a catalyst for the marriage boom among mid-lifers.

'The recession has left everyone feeling a little insecure,' she says. 'It's quite natural to hanker after the comfort and security that marriage can bring. When times get tough, there's always a return to traditional values.'