I was travelling on an Irish Passport card. An immigration Officer was unsure what it was and got his superior out. He then told me I could not travel in the UK on the card, that I needed a passport book which I did not have on the journey. I was travelling with my two children who were very upset as they also threatened to send us back to Germany.
I could not use my mobile phone at passport control but when I checked the Irish embassy website later the Irish passport card is valid for travel in the EU, UK, Switzerland and Norway.
I, and my children, felt harassed, embarrassed and upset by the experience. Then to find out that the immigration officer was actually were wrong about the issue made it even more frustrating.
Add to that the superior was apparently not familiar with the fact that Northern Irish citizens are entitled to hold Irish passports.
I was asked to explain why I travel on an Irish passport and not a British one.

Hey Seanna, that's absolutely terrible. "If you are an EU national, you do not need to show your national ID card or passport when you are traveling from one border-free Schengen EU country to another. " clearly the case. Any eejit should know this that staff at Heathrow don't is astounding. I hope you got the names of the employees who are responsible. I am very sorry that they treated you so poorly and dashed your plans. No doubt costing you money too.