"the great trust he held..."
See in text (Book the Third: The Track of a Storm - Chapter III)
Dickens is likely engaging in wordplay by using the noun “trust” here. Mr. Lorry, a strict man of business, often acts as a trustee for his clients. (He manages assets on behalf of a third party beneficiary.) His relationship with Tellson’s Bank resembles that between a trustee and a beneficiary; therefore, it is crucial that he avoid endangering the Bank by allowing Lucie and her daughter to stay under its roof.