Can I enter the duty-free shop at London Heathrow Airport without checking in?

No. Duty-free shops at the airport are only available after you have passed the border control. You have to go through security at London Heathrow Airport to enter the duty-free shop. Immigration procedures: When queuing up for immigration procedures, put the immigration card in your passport and give it to the immigration officer. After completing the immigration procedures, go to the terminal to take out your checked baggage, and then you can enter the country smoothly after undergoing customs baggage inspection.