1. Introduction

2. Gaia-ESO survey spectroscopy
2.1. Target selection and observations
2.2. Data Reduction
2.3. Radial velocities
2.4. Lithium equivalent widths

3. Membership selection

4. Results and Analysis
4.1. Modelling the radial velocity distribution
4.2. Two populations in the Gamma Vel cluster?

5. Discussion
5.1. The core-halo scenario
5.2. The captured cluster scenario
5.3. The cluster plus association scenario
5.4. The age puzzle

6. Summary