Madeleine McCann's parents have told the BBC they will do "whatever it takes, for as long as it takes" to find their missing daughter.
Next week sees the 10th anniversary of her disappearance, aged three, from an apartment in Praia da Luz in Portugal.
The couple, from Rothley in Leicestershire, said "real progress" had been made by the Metropolitan Police over the past five years.
"There is still hope that we can find Madeleine," Kate McCann said.
She has described the impending anniversary of her daughter's disappearance as a "horrible marker of time, stolen time", but said she was no less hopeful of finding Madeleine than she had been in 2007.
The search for Madeleine
Madeleine's father Gerry McCann said he and his wife "tried everything in our power to not have a long, protracted, missing person case like this".
"It's devastating and we really threw ourselves into trying to do everything we could to help find her," he said in an interview with Fiona Bruce.
"It looks like that hasn't worked yet. But you know we are still looking forward... we still hope.
"Since the Metropolitan Police actually started their investigation, it has taken a huge pressure off us, individually and as a family.
"The key thing was - and I suppose the injustice of it - was that after the initial Portuguese investigation closed, essentially, no-one else was actually doing anything pro-actively to try and find Madeleine.
"And I think every parent could understand that what you want - and what we have aspired to - is to have all the reasonable lines of enquiry followed to a logical conclusion."
Mrs McCann said the Met Police had "managed to pull so much together and sift through so much information, so now we do seem to be on just several lines of enquiry rather than tens, hundreds".
The money spent on the search
Four detectives are working on the case in the UK, scaled back from 30 in 2011, with more than £11m spent so far.
In March, police were granted £85,000 to extend the search for a further six months, from April to September.
Mr McCann said criticism of the amount of money being spent on the search was "really quite unfair" and that even though it was a single missing child, there were other crimes that came to light following Madeleine's abduction, that involved British tourists, "so I think prosecuting it to a reasonable end is what you would expect".
He added that this type of "stranger abduction" was "exceptionally rare", which was partly why Madeleine's case had attracted so much attention.
The McCanns also said they intended to continue a legal battle against Portuguese former detective Goncalo Amaral, who wrote a book about their daughter's disappearance, in which he suggested the couple had faked her abduction.
Although the book was banned by a Portuguese court, that decision was overturned by the country's highest court.
Mr McCann said they would be appealing, "because the last judgment, I think, is terrible".
He pointed out that Met Police chief leading the investigation, Mark Rowley, had recently said that there was no evidence that Madeleine was dead, "and the prosecutor has said there's no evidence that we were involved in any crime".
"Saying anything opposite isn't justice, it's not justice for Madeleine."
Mrs McCann said Mr Amaral's claims had caused "a lot of frustration and anger", but "we just need to channel that and... hope that in the long run that justice will prevail".
Negative public reaction
The McCanns have faced a barrage of negative comments on social media, and Mrs McCann said it was an area they both now avoided.
"We don't go there, to be honest. We are aware of things that get said because people alert us to them. I guess our worry is for our children."
She said she had found some of the online criticism shocking and an "aspect of human nature that I hadn't really encountered before".
"It's been striking and quite hard really to get your head round. Because why would somebody write that? Why would somebody add to someone's upset - why would someone in a position of ignorance do something like that?"
However, the McCanns said the main thing they had experienced "is the goodness of people and the support that we have had over 10 years, which hasn't wavered in all that time".
Mr McCann said they had "seen the worst and the best of human nature. And our personal experience, rather than on the internet, has been overwhelmingly seeing the better side of human nature."
Adapting to a 'new normality'
Mr McCann said that, before Madeleine was taken, they felt they had managed to achieve a "little perfect nuclear family of five" - the couple also have twins.
"Unfortunately for us, a new normality is a family of four. But we have adapted and that's important.
"The last five years, in particular, has allowed us to really properly devote time to looking after the twins and ourselves and of course carrying on with our work.
"At some point you've got to realise that time is not frozen, and I think both of us realise that we owed it to the twins to make sure that their life is as fulfilling as they deserve."
Living without Madeleine
Mrs McCann said she still buys birthday and Christmas presents for Madeleine.
"I obviously have to think about what age she is and something that, whenever we find her, will still be appropriate. so there's a lot of thought goes into it.
"But I couldn't not, you know; she's still our daughter, she'll always be our daughter."
A former GP, said she had now returned to work but in a different area to general practice.
"I think we don't dwell too much on things unnecessarily, so I think that's probably a self-protective thing there as well. We do have a very full life and as normal as we can make it.
"I think every kind of event that we do, whether it be a birthday or a family occasion or even an achievement or something - that is kind of when you really feel her absence.
"It's slightly different to how it was in the early days, when everything we were doing was to find Madeleine, whereas now we are having to get on and live a life as well, but it's not like any day she's not there, if you know what I mean."
Keeping up hope
Mrs McCann said she once felt embarrassment when people discussed the amount of money being spent on the search for her child, but then realised that other big cases also cost a huge amount of money.
She said one positive was that it made people more aware of the issue of missing children, and other families of missing people "have had more support from each other" as a result.
Mrs McCann said she also wanted to reassure supporters that progress was being made.
"It might not be as quick as we want, but there's real progress being made and I think we need to take heart from that, and we just have to go with the process and follow it through - whatever it takes, for as long as it takes.
"But that there is still hope that we can find Madeleine."
There will be a BBC Panorama programme Madeleine McCann: 10 Years On on Wednesday at 21:00 BST