The rules and regulations of the interweb!!!!!!!
The age of ciminal responsibility is 10 years old which means any means of crime you do online when your above the age of ten can be prosecuted. If the child is under 10 years old the childs parents is held responsible for this as they have not been taught right.
Age of consent
According to the Sexual Offences Act 2003 says that anyone under the age of 16 cannot consent to sexual activity. The law says that someone of this age cannot have sexual intercoure with anybody who is younger than the age of 16. Anyone who is doing this may be prosecuted. Even if both people are under the age of 16, you can be prosecuted. This might include being put on the sex offenders register and getting a criminal record.
It is against the law as whoever has that picture on their phone, is technically in possession of an indecent image of a child. If the people involved in sexting are under 18, this is illegal (even if the person is your boyfriend or girlfriend). This means that person can be prosecuted under the Sexual Offences Act 2003.