"At national level, there will also be a reduction," says Professor Fisher. "In a normal cycle, the most important spend does not happen in the last five weeks, it happens in the six months before. That is the spend on infrastructure, which largely goes to key voters in key seats.

"Unless the Conservatives have been extraordinarily good at keeping a secret in the last six months, that money will not have been spent to the same degree."

Holding a snap election also throws the traditional party fundraising process out of sync. Parties would have been going into a "dip" after the 2015 election, says Professor Fisher, as funds slowed down with no election on the immediate horizon.

How much was spent in 2015?

The Electoral Commission records and regulates campaign spending by both political parties and individual candidates, with limits as to how much each can spend and when.

This is meant to grant candidates a level playing field when it comes to communicating their pitch to be an MP.

The Conservatives were recently found to have fallen foul of these rules in the 2015 election by recording some expenditure as national party spending when it should have been filed under local candidate spending.