Detailed Instructions: Given a travel related situation, and given a specific question about the situation, summarize the question into a title
Problem:I have dual citizenship. South African and Dutch.

I am traveling from Amsterdam via Heathrow to Nairobi Kenya.

I have exited Netherlands on my Dutch passport, but was warned not to show my South African passport at Heathrow.

I do not need a visa if I enter Kenya on my South African passport.

Should I be worried about this warning? And what should I do when asked for my visa at Heathrow(I don't have one)?

Solution:
Dual Citizenship Question Netherlands to Kenya