Why does dr manette agree to destroy his bench and tools?

"I would not keep it," said Mr. Lorry, shaking his head; for he gained in firmness as he saw the Doctor disquieted. "I would recommend him to sacrifice it. I only want your authority. I am sure it does no good. Come! Give me your authority, like a dear good man. For his daughter's sake, my dear Manette!"

"In her name, then, let it be done; I sanction it. But, I would not take it away while he was present.

Let it be removed when he is not there; let him miss his old companion after an absence."