Banco Eye Tap Leaking From Swivel Base When Stem is Turned Drainage and wastage systems and plumbing help, advice and answers

[DIYtomTOM]

Our banco eye kitchen mixer tap has started to leak from the swivel base when the stem is turned anti-clockwise to the right and is stopped when turned to the left. Is this a simple replace washer repair? The tap is around 4 years old

Thanks for any help you can give