Under English law, a person can write instructions for the distribution of her property upon her death; then, when that person dies, the probate court will implement these instructions to convey the property of the estate to the correct heirs. These written instructions are called the decedent’s “will.” You might write in your will that you want your money to be distributed to your children in certain amounts, or given to a charitable cause; you might want certain possessions to go to certain people who would be likely to appreciate them, or to a museum or library. The person writing the will may leave the will with her lawyer or with other important papers (such as insurance or banking records) or make whatever provision she likes to see that her will comes to light when it is needed.
If you write a will and then survive the writing for long enough, your wishes may change, or you may lose or gain property in such a way that you want to write further provisions, called a “codicil.” This allows you to make small changes while sparing you the trouble of starting again with a new will.
Christopher is saying that someone has died, having a written a simple will with no codicil. A complicated will with a lot of codicils might spend a long time in probate, as potential heirs argue about contradictions or ambiguities in the writing in an effort to take part of the estate. The solicitor told Christopher that this will is simple. But Christopher has some experience with probate, and in his experience the probate court can spend a year executing a simple will; perhaps they spend much longer than a year executing a complicated one. So, he says that knowing “them,” that is, knowing the officers of the court in the sense that he knows the way they conduct the business of the court, that will mean at least one year of administration.
Christopher’s comment sounds sarcastic. He seems to express contempt for the court, in that common sense would suggest that a simple will should be discharged in much less than one year.