It is not unusual for airlines to advise passengers who are traveling with children to obtain a notarised consent from both parents, even if the accompanying adult is one of the parents. This has resulted in travellers spending money on legal paperwork that they probably do not need.
There are certain countries that have strict procedures in place regarding taking children out of that country. South America and Eastern Europe are particularly stringent on ensuring that children with that nationality are not being taken out of the country without the express permission of both parents. However, it is unlikely that a British citizen travelling with his/her British child would have any difficulty, unless the child has dual nationality.
Grandparents travelling without either parent should err on the side of caution and it seems that fathers travelling with their children without their mother are more likely to have to answer questions at the airport. A teenaged minor travelling without either parent should carry a notarised consent to avoid any difficulties in foreign airports.
A notarised consent from The Notary Solution will cost £80 plus VAT and will also grant the accompanying adult the power to consent to emergency medical treatment.
In essence, we do not consider that a notarised consent is required in every case but may be necessary or beneficial for specific situations. We are happy to advise on whether we think a notarised consent should be obtained so that you have sufficient information to enable you to make a decision.