Correct Food Allowance - Private Hire Drivers / Taxi Drivers in London

From my understanding as a self employed private hire / taxi driver you would be able to claim an expense for food purchased whilst out working. Do you have to be a particular distance from home or on what basis would it be acceptable to add this to your expenses and how much. I have seen online that self employed people may claim £10 per day (£5 per 5 hours worked) and elsewhere I have seen you can claim for £20 if worked for 15 hours+ not sure what is the correct rate? I wanted to Clarify: 1. How much is the allowance that an individual in the above position can claim and on what hours worked (minimum and maximum daily) 2. Do they have to be a in a particular distance from home because as a driver you end up anywhere and everywhere and not always able to bring lunch with you so any distance or other requirement 3. If your receipt for food is greater than the allowance are you still able to claim the allowance amount. Say £5 for 5 hours were correct and you worked 5 hours however had lunch for £10, can you use £5 from this £10 receipt as an example or would the lunch have to be exactly £5 or less to qualify. Another example if the 15 hours - £20 limit above was correct above and your meal came to £25 would you be able to use £20 of this receipt or would this £25 lunch receipt now be void/unusable as it is over the £20 limit.

Hi ali oz,
You cannot claim the cost of food for normal substinance as we all need to eat and drink.
Please refer to:
BIM37920 - Wholly and exclusively: expenditure having an intrinsic duality of purpose: food and drink
Thank you.