The pound has been under pressure in volatile trading as Theresa May fired the starting gun on the marathon two-year process for the UK to formally leave the EU.
Sterling was nearly half a cent lower against the US dollar at $1.24 by late afternoon on Wednesday though it was slightly higher versus the euro.
The UK currency saw ups and downs over the course of the session amid intense focus on the formal start of the Brexit process.
Early on, it slipped against the dollar and the euro in Asian trading ahead of the Prime Minister's announcement.
The pound fell below $1.24 - leaving it more than half a cent lower against the greenback.
But by the time of the stock market close it had turned negative again.
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The pound's value has collapsed against a basket of major currencies since the referendum vote last June.
The decline - by up to 20% against the dollar alone - has had several effects with the impact taking some time to be fully realised.
While it has made goods from abroad more expensive - filtering through to shop and other prices - it has also resulted in UK produce becoming more attractive overseas.
As UK holidaymakers notice higher in-resort costs while on holiday, tourism figures show a benefit from an influx of visitors to the UK - lured here by their money going further in shops, restaurants and at attractions.
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Market analysts said that some of the early pressure on sterling on Wednesday was down to dollar strengthening but the shift also reflected uncertainty ahead as negotiations with Brussels on the terms of Brexit prepare to get underway.
The weakening aided a rise in the FTSE 100, and it closed 0.4% higher.
A lower pound helps many its constituent companies which sell their goods and services in dollars - netting a currency benefit when those sales are booked in pounds.
Sterling remains 17% down against the dollar and 15% lower versus the euro since the Brexit vote.
Neil Wilson, senior market analyst at ETX Capital, said: "A truly hard Brexit has not been priced into sterling. We could see it move lower still if negotiations take a sour turn - 1.10 US dollar is feasible."
Kathleen Brooks, research director at City Index, said: "Looking ahead it is not Article 50 that should concern the markets, but rather the response from the Europeans.
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"Two dates to watch out for include: 4 April and 29 April, when the EU's response to the UK's triggering of Article 50 and the first EU Brexit summit take place, respectively.
"This should give the market a sense of the tone of the negotiations, and whether the EU will want to work with the UK to give them a good deal, or if they want to punish them for deciding to leave.
"Obviously, the latter would be a big negative for the pound."