Which borough of London has the cheapest roast dinners?

The average price in Croydon is £16.68 (5 reviews)
The average price in Lewisham is £17.28 (9 reviews)
The average price in Richmond upon Thames is £17.43 (10 reviews)
The average price in Merton is £17.58 (6 reviews)
The average price in Wandsworth is £17.73 (15 reviews)
The average price in Hounslow is £18.68 (5 reviews)
The average price in Hackney is £18.81 (28 reviews)
The average price in Camden is £19.49 (40 reviews)
The average price in City of London is £19.62 (16 reviews)
The average price in Kensington & Chelsea is £19.75 (17 reviews)
The average price in Lambeth is £19.75 (22 reviews)
The average price in Tower Hamlets is £19.86 (19 reviews)
The average price in Waltham Forest is £20.26 (9 reviews)
The average price in Southwark is £20.38 (29 reviews)
The average price in Haringey is £20.42 (6 reviews)
The average price in Islington is £20.42 (25 reviews)
The average price in Hammersmith & Fulham is £20.92 (13 reviews)
The average price in City of Westminster is £22.71 (47 reviews)