Christine Northam, a counsellor working for Relate, said: "On these websites you have to give details, and I wonder whether the matching might eliminate some potential future problems before you even get going with the person, whereas when you meet naturally a powerful initial attraction might mask problems in the future."But Mr Marshall warns of the pitfalls: "I think the problem with meeting someone online is that you don't have any context for them.
Sheila Philips from Scotland and Kevin Stephenson from Greater Manchester met on a multiple sclerosis community board and married in 2003.
Louise Wright, 29, then of Bristol, met her partner through a dating service for people interested in horses.
And second there are what you might call computer-assisted relationships, where online dating sites match people after they've completed a questionnaire.
Shared values and aspirations are given far more weight than liking the same kind of music or both being into, say, cycling.
Andrew G Marshall, a leading marital therapist, said that "30s and 40s are the key internet daters who end up in my office. People will say 'Oh, we clicked because we both liked cage fighting,' and that's fine, but to make a successful relationship you need more than common interests."But whether a successful relationship came via self-started online encounters or dating sites, many happily hitched people told us that it was vital that they had a lengthy "getting to know you" period of emails and phone calls before they met face to face.
Arthur Ritson, 43, from Bath, and Ann Ramsay, 34, from Edinburgh, who married in 2001, met online and emailed each other for three months before meeting.
And Rachel Lilley, 33, and Nigel Evans, 35, said they talked on the internet for a year before marrying in 2005.
Many couples felt that online dating took some of the "hit and miss" out of meeting a partner.
In 1995, local newspapers started reporting the first weddings of couples who, they revealed with breathless amazement, "ACTUALLY MET ON THE INTERNET! No setting eyes on someone before you asked them out. Today, partnerships made on the internet are not only commonplace, but fast becoming the standard way you meet your future spouse.
No sly glance across a crowded room, no awkward conversation steered round to that coy invitation for a first date.
New research shows that more and more couples are meeting online and marrying.