It seems like the world has gone consent-mad at the moment, with even the aliens in Doctor Who unwilling to take over the world without our explicit prior consent. (See for yourself…)
In research it is “fundamental”  that people agree to participate, and fully understand what they are getting into i.e. they give ‘informed consent’. And while it’s now generally agreed that including children and young people in research is important, it’s also recognised that cognitive ability and understanding can vary considerably from person to person, even at the same age [1, 2]. So where does this leave us?
To consent to medical treatment, all you need is the ability to understand what you’re agreeing to, and it’s recognised that this is possible before the age of 16 (‘Gilick’ or ‘Fraser’ competence). Though there is no legal precedent or statute for participating in research, these principles are expected to apply . So while technically it should be enough for just a patient under 16 to agree to participate (as long as they are capable of understanding), in practice, you’ll ‘underpin’ this by taking consent from their parent or “legally authorised representative” .
However, don’t get caught out! While the biological mother has parental responsibility for their child “automatically” and can consent for them, the same is not true for the biological father ! Though they often do have parental responsibility, through being married to the mother or having their name on the birth certificate, and so on, this is not always the case! (To cover this in more depth, BCH has online Informed Consent training available on their intranet.) With my project, I found having a decision tree to ensure that the father has capacity to give consent for their child invaluable, though I would recommend at least having a list of questions to check before you have them sign. It would be a shame to have them waste their time (and yours) providing data that you can’t use…
 Modi et al. (2014) ‘Guidance on clinical research involving infants, children and young people: an update for researchers and research ethics committees’, Archives of Diseases of Childhood, 99 (10), pp.887-891. http://dx.doi.org/10.1136/archdischild-2014-306444
 Farre et al. (2016) ‘Health professionals’ and managers’ definitions of developmentally appropriate healthcare for young people: conceptual dimensions and embedded controversies’, Archives of Disease in Childhood. http://dx.doi.org/10.1136/archdischild-2015-309473
 Department of Health. (2000) Consent – what you have a right to expect: A guide for parents. London: Department of Health.