Essex Road to Highbury & Islington without Oyster is £4 - for a 2-minute journey.
It's an Anytime Day Single (SDS), which others have given examples of.That's not an Anytime Single though.
Greenfield - Marsden surely?
Clapham High Street to Wandsworth Road takes 1 minute and costs £1.80.
Wow nice one! Although that fare comes into scrutiny as it isn't proportional to the cheaper Oyster fare (£1.30)
If the tube counts....?? the £4 for the 0 secs Leicester Square to Covent Garden is approx £8.00 per min. Bargain.
It takes longer to go down the escalators than it does to walk between the two.