Questions have arisen over how calm the couple have remained and how Kate, in particular, has come across as cold and unwilling to discuss her feelings. Some have queried whether it was normal for Kate to go running the day after Madeleine went missing, while others have maintained that the massive publicity drive undertaken by the McCanns has not been in keeping with the behaviour of a couple who have just lost a child.

Is this simply a case of 'cherchez la femme'? Lindy Chamberlain was wrongly accused of murdering her baby in the 'dingo baby case' when police couldn't find any other suspects. British woman Joanne Lees was also wrongly implicated in the murder of her boyfriend Peter Falconio in Australia and vilified by the media for wearing a 'cheeky monkey' t-shirt to a press conference. Could the same thing be happening again with the McCanns, and to Kate McCann in particular?

According to Patricia Casey, professor of psychiatry in UCD, how a person reacts to the loss of a child and how their grief is expressed varies widely from person to person.

"Grief can lead to sadness and anger as well as shock, numbness and feelings of self-blame, " she said.

"But crucially, some people don't show their grief publicly. Not everyone bursts into tears when they're surrounded by others, but instead will do it in the privacy of their own home. It certainly doesn't mean they are feeling their grief any less and it's important to remember that."

The disappearance of a child is, according to Casey, "the most difficult situation of all". "The grief at the loss of a child is greater than the loss of an adult anyway, " she said. "But the disappearance of a child is incredibly hard on the parents. They don't know whether to grieve fully and pass through it, or to continue to hope and worry about how their child is. It's a real limbo situation."

Psychotherapist Colman Noctor believes it is possible the McCanns have distanced themselves from the reality of what has happened as a way of coping with Madeleine's disappearance.

"After a death, a person will often enter a mechanical state that allows them to get through the funeral before acute grief reactions set in, " he said. "The McCanns have always given the sense of being very strong and managed the business end of finding Madeleine almost like one would manage a funeral. I think they are disconnected from the event and the emotional sadness and that's their way of coping."

Kate McCann's jog after Madeleine's disappearance can also be put down to a mechanical reaction to grief. "No matter what the outcome is, this is a couple who are suffering from the loss of a child, " Norton said. "And, regardless of how Madeleine disappeared, there is a huge amount of guilt attached to it. I think they are going through a process known as reparation . . . their pledge to stay and never give up the fight and their visit to the Pope are all ways of dealing with their grief and guilt."

Cuddle Cat, Madeleine's favourite toy, has stayed prominently with Kate McCann since her child's disappearance, which, according to Noctor, is probably a sign of her attempt to reconnect with Madeleine.

"Death is a necessary closure in life and without it, there is a constant persecution of thought, " he said. "Without that closure, there is a constant uncertainty that a person will find very hard to get over."

After the death of a child, a parent's grief can often become abnormal, said Casey. "Abnormal grief can occur if a person doesn't accept the death in any way. They may still set the table for them at dinner, or celebrate their birthdays or keep their bedroom exactly like it was when they died."

But the McCanns may never have a chance to work their way through this grief if Madeleine is never found and while public scrutiny continues to glare over them.

"People will always be judgemental of others who are grieving, " said Noctor. "There is a belief that you have to be constantly melancholic for a long time. But it doesn't necessarily work that way. You don't have to maintain the same level of upset for a long time in order to grieve fully."

"Grief is a personal but also a cultural thing, " added Casey. "In the UK, they tend to be even less obvious and display a reserved kind of grief. It doesn't mean their grief is less than others."