How do I ask for user’s first initial and full surname?

So trying to keep data and forms as clean as possible for a university project (online book store). As part of my designs I elected for a user's first initial and surname to address them (e.g. J Smith for John Smith), the app has no requirements for a global populace, so focusing on a UK audience.

What's the simplest way of asking the user for the information in a form (preferably in one field)? Is Initial-Surname explicit enough if I provide an example in/around the input field? Or should I do more work to split the fields and then concatenate after?