Has anyone had a problem with travel with kids who don't have your last name?

[Louw12345]

Heard about this law or something that if a child has a different last name to you even though you are their parent you need a letter of permission to travel from the parent that has the same name.
Can anyone advise me of this?

Take their birth certificates with you, I've had to produce my DS's every time we've come home and passed through UK immigration.
Some countries will want a letter/document of consent from the other parent as well, but not usually if you're travelling within Europe. If your ex, like mine, won't do this it's lieu worth applying for a specific issue court order which will give you permission. Mine has a statement implying permission for future holidays as well. Sounds daunting but it's easy to do yourself; print forms off online, and fees can be waived if on low income/benefits.