In detail
A £10 free bet on a 2.0 selection returns £10 in winnings if the bet wins, not £20 — the £10 stake is not yours and is not returned. This makes free bets less valuable than they appear: a £10 free bet at evens is roughly worth £5 in expected value, before considering minimum-odds restrictions and expiry. They typically require a qualifying real-money bet first and carry minimum-odds restrictions.