However, later on Wednesday sterling jumped to as high as $1.2865 after an opinion poll from Panelbase gave the Conservatives a 15-point lead over Labour. While not completely discounting it, Brooks did say she would take this report "with a pinch of salt".
But the Prime Minister's apparently commanding poll lead over Labour has since narrowed, reducing expectations of a landslide victory.
Commentators have been skeptical of the modeling, given how far the projection deviated from other polls, which show the Conservatives with a significant, albeit shrinking, lead.
"Less than 3 weeks ago May averaged an 18pt lead". He said if Brussels was watching, would the European Union think that she is a " blowhard who collapses at the first sign of gunfire".
He states: "The idea behind MRP is that we use the poll data from the preceding seven days to estimate a model relating interview date, constituency, voter demographics, past voting behaviour, and other respondent profile variables to their current voting intentions".
YouGov's forecasts is controversial, though, as polling companies don't usually produce these kind of seat-by-seat projections.
However, until now no poll has suggested that the Conservatives could lose their majority in parliament.
Labour leader Jeremy Corbyn said the manifesto would create a "war between generations" if implemented.
"While Labour's tax and spending plans are unlikely to win any friends in the financial sector, the party's more sanguine stance towards striking a trade deal during the Brexit negotiations might find common ground with some City grandees", she wrote.
Jupiter Asset Management said the fall in sterling reflects concern that the Tories "may not quite achieve the overwhelming majority it needs to play a strong hand in the Brexit negotiations", with markets "clearly pricing in" a more modest majority than earlier in the campaign. "But the Conservatives' lead has more than halved in recent polls", Kallum Pickering, senior United Kingdom economist at Berenberg, said in a note.
In a constituency-by-constituency projection by YouGov for The Times the Tories are set to win 310 seats which is short of the 326 seats required to form a Government and 21 fewer than secured by David Cameron's successful General Election in 2015.