Connector comprising - a housing, - a mate-assist lever articulated on the housing, about an axis of rotation, between at least one open position, in which a counter-connector can be coupled to the connector in a coupling direction substantially perpendicular to the axis of rotation of the lever, and a closed position, in which the connector and the counter-connector are coupled together, - primary locking means (19, 20, 21) for locking the lever in the closed position; - secondary locking means of the lever movable between a locking position in which the secondary locking means of the lever co-operate with the primary locking means (19, 20, 21) to lock the lever in its closed position and an unlocking position in which the secondary locking means of the lever release the lever to allow the lever to rotate about the axis of rotation, towards its open position, and in which the secondary locking means - cannot be moved from their unlocked position to their locked position when the lever is in the open position, and - can be moved from their unlocked position to their locked position after rotation of the lever from its open position to its closed position, characterised by the fact that the secondary locking means are configured to be able to occupy a delivery position, distinct from the locking and unlocking positions, in which the lever can be in the closed position without being locked by the secondary locking means, and in which the secondary locking means are not under constraint from either the housing or the lever. - a housing, - a mate-assist lever articulated on the housing, about an axis of rotation, between at least one open position, in which a counter-connector can be coupled to the connector in a coupling direction substantially perpendicular to the axis of rotation of the lever, and a closed position, in which the connector and the counter-connector are coupled together, - primary locking means (19, 20, 21) for locking the lever in the closed position; - secondary locking means of the lever movable between a locking position in which the secondary locking means of the lever co-operate with the primary locking means (19, 20, 21) to lock the lever in its closed position and an unlocking position in which the secondary locking means of the lever release the lever to allow the lever to rotate about the axis of rotation, towards its open position, and in which the secondary locking means - cannot be moved from their unlocked position to their locked position when the lever is in the open position, and - can be moved from their unlocked position to their locked position after rotation of the lever from its open position to its closed position, - cannot be moved from their unlocked position to their locked position when the lever is in the open position, and - can be moved from their unlocked position to their locked position after rotation of the lever from its open position to its closed position, characterised by the fact that the secondary locking means are configured to be able to occupy a delivery position, distinct from the locking and unlocking positions, in which the lever can be in the closed position without being locked by the secondary locking means, and in which the secondary locking means are not under constraint from either the housing or the lever.