How useful is Source A as as evidence about the electoral system before 1832?

[Source A]'The fact is that yesterday morning I was elected by one voter to represent this ancient borough in Parliament. There was no other candidate and no opposition. On Friday morning I shall leave this triumphant scene with a determination not to see it again in less than seven years.' From a letter sent by Sir Philip Francis in the early nineteenth century to a friend. Francis was MP for the borough of Appleby.This source is useful as it shows an MP's insight into the unreformed electoral system. We can infer from the references to 'one voter' and 'no other candidate and no opposition' that Appleby was a pocket borough, one controlled by the local landowner. Pocket boroughs persisted even though 'new towns' like Manchester had no MPs of their own.Secondly this source is also useful because of its date. It is from the period just before the 1832 Reform Act, showing historians some of the things that were being criticised by reformers. Getting rid of pocket boroughs like this one was one of the aims of the reformers and of the Act. So this source is very useful in telling us what was wrong with the electoral system and why there was a growing demand for reform. However, there are also limits to the source's usefulness. It does not tell us about other problems like large cities not having their own MPs, or the lack of a secret ballot.