Self employed tour director / manager - subsistence expenses

I am a self-employed (sole trader) tour manager, leading groups on tours. I travel with the groups when we are on tour to different parts of the UK & Ireland. I am invariably away from home, as we are travelling on a group educational tour/holiday. Am I am able to claim subsitence costs during these travels against my income? (the client pays an allowance, which is taxable, for each meal that not included in the group tour, and I then buy my own food for that meal - mainly lunches, occasionally also dinner). Thank you

Hi JAHOUL,
Please refer to guidance here:
Expenses if you're self-employed
Thank you. 

Thank you so much for this helpful link. To be sure of my understanding - as I am away on business when I am on tour (staying overnight for the sole purpose of the tour) then I am able to claim reasonable costs for each meal (breakfast, lunch, dinner) that I do not take with the tour group as a tour activity. Is that correct? Also, how do the rates I have seen of £5, £10, £25 relate to any costs that I can claim for such meals? I appreciate that I should retain receipts for any such meals that I look to claim as business expenses, but do these rates indicate the maximum I can claim for each of the meals involved, or do they apply in different scenarios to this (in which case, I'd appreciate if you can clarify). Kind regards,

Hi JAHOUL,
These rates are the benchmark rates for meal allowances for an employee and can be found here:
https://www.gov.uk/hmrc-internal-manuals/employment-income-manual/eim30240.
They are the maximum tax and NIC free amounts that can be paid by employers, who choose to use the system.
An employer can pay expenses higher than these amounts, but the excess should be charged tax and NIC.
 If you are self employed, you can claim expenses for meals on overnight business trips.
Plesae have a look here:
BIM47712 - Specific deductions: travel and subsistence: living expenses abroad — foreign trades 
Thank you.