Here's why Brexit Britain might be unable to reach a deal with the EU in two years

UK PM May has buckled to the pressure of her own party: Nick Clegg

U.K. Prime Minister Theresa May pulled the Brexit trigger on Wednesday and kick-started a two-year countdown for Britain's departure from the European Union though Britain's former Deputy Prime Minister argued there was "absolutely no way" the U.K. could secure everything in such a narrow timeframe.

A handwritten letter notifying the U.K.'s intention to leave the EU was delivered to European Council President Donald Tusk on Wednesday.

May's letter on behalf of the U.K. government signifies a two-year withdrawal process in which midnight March 29, 2019 has officially become the deadline for Britain and the EU to agree on a divorce deal.

"(As well as a divorce deal) you then negotiate the most complex free trade agreement that probably the developed world has ever seen, you have to negotiate new crime fighting arrangements, new arrangements on the environment, you have to negotiate with over 50 other countries with whom we have trade relations by way of our membership to the EU and… and on top of that, you have to have it all ratified not only by (Westminster) but by 27 parliaments and possibly some regional parliaments across the EU," Nick Clegg, former deputy prime minister, told CNBC outside Westminster on Wednesday.

'Something's got to give'

Being honest about Brexit challenges is not being gloomy: UK lawmaker

Clegg also rather ominously predicted "something's got to give".

The two-year time limit can, in theory, be extended although the unanimous consent of Westminster as well as the European Council, which is made up of 27 member state leaders, would be required.

Given Europe's heavy political calendar, in which the key EU member states of both France and Germany have general elections scheduled, and European Parliament's demands for time to be allowed to vote upon a potential deal, it appears the timeframe for the U.K. government is closer to 18 months rather than two years.

"There is a lot at stake and 18 months is actually a very short (amount of) time," Hilary Benn, chair of the Brexit select committee, told CNBC on Wednesday.

"Being honest about the challenges is not being gloomy, it is doing our job as parliamentarians because this is a really, really important moment for the future of the country," Benn added.

'No such thing as hard-Brexit'

'Hard Brexit' an invention of those who cannot recognize result: Nigel Farage

May previously declared the U.K. would be better placed with no deal as opposed to a bad deal with the EU and critics suggested the prime minister was in favor of a so-called "hard-Brexit".

EU diplomats contested the viewpoint Britain would be better off without a deal and pointed out the U.K. would then fall under World Trade Organization rules. In this event, U.K. firms would face tariffs on most goods and the economy as a whole would likely suffer significantly, EU leaders argued.

"Hard Brexit is an invention by those who simply can't recognize the referendum result. Let's be clear, we voted to leave the EU," Brexit proponent Nigel Farage told CNBC on Wednesday.

"The strength of (the U.K.'s) position is this, no deal is better for us than the current deal we have got… When you start from a position where the worst-case scenario is better than where you are now, it's not all bad," Farage concluded.

Tusk has previously said he and the EU would be prepared to officially respond within two days of receiving the multi-page document. Though at around 1.40 p.m Brussels time, he said via Twitter "after nine months, the U.K. has delivered Brexit" and was subsequently pictured with the signed letter from May.

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