Can a surety be bound to the letter of their agreement if the surety has been altered in a single line?

In Blest v. Brown (1862), 4 De G.F. & J. 365 at p. 376, 45 E.R. 1225 at p. 1229, Lord Westbury L.C. said: It must always be recollected in what manner a surety is bound. You bind him to the letter of his engagement. Beyond the proper interpretation of that engagement you have no hold upon him. He receives no benefit and no consideration. He is bound, therefore, merely according to the proper meaning and effect of the written engagement that he has entered into. If that written engagement is altered in a single line, no matter whether it be altered for his benefit, no matter whether the alteration be innocently made, he has a right to say, "The contract is no longer that for which I engaged to be surety; you have put an end to the contract that I guaranteed, and my obligation, therefore, is at an end."