The remedies, and why they are so strong
Three things become available once arrears have persisted for the statutory period. The owner can sue for the money, which is the ordinary and least alarming route. They can enter into possession of the property and take its income until they are paid. And they can grant a lease over the property to a trustee, who can raise the money owed by mortgaging or letting it.
These remedies date from a time when a rentcharge was a meaningful income stream, and they were written to protect it. Applied to a debt of a few pounds, they are wildly out of proportion — and nothing in the statute scales them to the sum involved.