There's currently no UK law regarding tyre age, although there is a consultation currently ongoing in regards to banning tyres older than 10 years old on HGVs and buses. Black Circles says tyres are considered to be fit for retail up to 5 years from the date of production. When in use, it is recommended that tyres are replaced when they reach 7 - 10 years old, (6 years in the case of caravans or trailers).

Rubber degrades with age even if the tyres aren't used very often (or at all). So, while it isn't illegal to use this tyre, I would have a good look at it to see if you can spot any age-related damage, though there may be some that you can't spot internally. Continental does say to replace tyres after 10 years, as well as checking the manufacturer guidance on your vehicle. In any case, most tyres will likely need to be replaced for worn treads or for other reasons before any recommended age.