Traditionally one seat was as a rule conceded to the Castle interest of the Percys, which from them passed to the 7th Duke of Somerset, and from him to the Wyndhams. The other seat was usually filled by representatives of gentry families owning property in the borough or its neighbourhood. The local gentlemen, who held most of the burgages, were long jealous of purchases by a single magnate which would ‘close the borough’ and deprive them of ‘mercenary respect’ at elections.

Sir Charles Wyndham, who in 1750 succeeded Algernon, 7th Duke of Somerset in his Cumberland estates and in the earldom of Egremont, inherited from him only eight burgages, but by 1756 had purchased a further 70 for nearly £10,000. In that year Sir James Lowther, 5th Bt., under the terms of Sir William Lowther’s will, acquired 24 burgages for £2,000; and set out to destroy the Castle interest.

The campaign began with a pamphlet1 accusing a ‘great and noble personage’ of scheming to close the borough, and calling on the burgage proprietors to preserve their rights or at least to ‘join all their burgages into one common flock, and set them up to the highest bidder ... who will not suffer them to go under the real value’. Next, on 17 Sept. Lowther’s agent openly entered the market, while claiming to do so in order to keep the borough free. He was authorized to offer £120 for each burgage, and to advance his price if Egremont offered higher. The proprietors showed great business acumen and held back their sales, but on 25 Sept. Egremont’s agent warned his master that he ‘must either purchase the borough at a most extravagant price or lose it for ever’.2

On 27 Sept. Lowther’s agents pulled off a master stroke—

having persuaded the common people that they were only to buy a certain number of burgages, and would then forbear, all the lower sort of burghers in town flocked in to them at once for fear the markets should fall ... above 15 of them contracted immediately and several others are going in today [28 Sept.]3

Egremont sent orders to spend up to £20,000 to purchase a clear majority, ‘but if that could not be effected at one stroke, he would not have a shilling expended as it would be thrown away’. These instructions did not reach Egremont’s agents in time. On 28 Sept., to stem the tide, they bought three burgages for nearly £1,000; and next, proposed to buy 20 for £10,000, which they thought would save the interest. But on 30 Sept. Thomas Simpson, Egremont’s chief agent, wrote to his master:

Very few of the common people are left unsold. ... Your Lordship’s own burgages and the votes of your friends, with Sir John Mordaunt and his friends, would still be an overmatch for Sir James, but now when prices are so high ’tis to be feared that the better sort will begin to sell.

Egremont had 78 burgages, Mordaunt 18, and Simpson reckoned 57 as belonging to Egremont’s friends; which gave him 153 out of 278 burgages. The price of a burgage was now £500, and Egremont’s friends began to sell to Lowther; nor could Simpson, without an order from Egremont to buy at that price, prevent them. By 4 Oct. Lowther had a clear majority, having in the last ten days purchased 134 burgages for a sum estimated at over £58,000.

On 27 Oct. Lowther wrote to his mother:4

I can now with pleasure tell you that we have the borough secure, for yesterday the finishing stroke was put to Lord Egremont’s interest without opposition. I mean the getting of the bailiff who is the returning officer. ... We have got one of our naming chose. ... All the people that are on their side (for most of Lord Egremont’s friends are come over to us) are afraid to show their faces and the cry is entirely for us.

Cockermouth remained under the control of the Lowthers until 1832.