Speaking to CNBC, she said: “I share the optimism that this City will remain the leading global financial centre in the future, that it is at the moment.
“But of course, things will change during the process of Brexit. We will be facing the world from a different position.
“At the moment it is clear firms are having to make arrangements for how to operate following our leaving Europe and we see signs one of two – a few jobs are moving.
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Catherine McGuinness said she was optimistic about the UK’s future after Brexit
“Well, people are setting out operations elsewhere. But we see no sign of massive moves from London.
“Very confident that if we move from politics to pragmatism and find a deal that works for this country and for Europe we will remain very strong, we’ll keep the strengths we have.”
Ms McGuinness said the two-year period set out by Article 50 was a short time to negotiate with Brussels, but added she was sure a good deal could be struck within the deadline.
The City boss said: “It is a short time frame and firms need to be sure that they can operate on day one as they are operating now.
We see no sign of massive moves from London
“They need to be able to serve their customers, but there is plenty of time to strike a sensible deal. Very much looking forward to us getting into that after the election.
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“Speaking to the sector it seems very clear to us there are three factors they particularly need; one is clarity, as I’ve already said, clarity and certainty as soon as possible.
“That would be reinforced by a transition or an implementation phase so that there is time to work through wherever is needed to get the ultimate deal that we reach.
“Second is access to people for the jobs. We’ve thrived on having access to the best possible people for the best jobs.
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“And finally, of course, is the deal we finally strike at the end which has to work for Europe as it does for us.”
Ms McGuinness added: “It seems to us the best solution would be an arrangement with full two-way access.”
Meanwhile, Roland Rudd, Chairman of Open Europe and Finsbury, told CNBC he was worried European Union bosses would adopt the “us VS them” attitude as well, as a result of Theresa May’s rhetoric.
The businessman said: “The best case would be to not take the best deal off the table prematurely, which is membership of the single market, continuation in the customs union, which is what the Conservatives are doing.
“And then the best case is some sort of free trade agreement but I am concerned the Prime Minister (has) identified the European Union leaders as the enemy, and that they'll see her as the enemy.”