Is this a once-in-a-lifetime opportunity to buy Barclays plc, Banco Santander SA and Shawbrook Group plc?

A superb opportunity

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Brexit has caused the share price of Barclays(LSE: BARC) to fall by around 28%. However, the bank was experiencing weak investor sentiment prior to Brexit, with its new strategy and subsequent dividend cut causing its shares to come under pressure in recent months.

While disappointing, this share price fall presents investors with an opportunity to buy Barclays at a time when it's trading on an ultra-low valuation. For example, it has a forward price-to-earnings (P/E) ratio of only 6.2, which indicates that an upward re-rating is very much on the cards. The bank's new strategy could be a catalyst for that, with Barclays now more focused on improving its balance sheet strength and in reorganising its asset base so as to become leaner and more profitable.

Such moves could convince the wider market that Barclays will survive any downturn resulting from Brexit, and while its shares could come under pressure in the short run, for long term investors I think the present time is a superb opportunity to buy in.

A star for the long term

Also falling post-Brexit have been shares in Santander(LSE: BNC), although they have been hurt in the last couple of years by weakness in another key market for the bank: Brazil. Looking ahead, Santander could continue to fall in the short run due to the potential for further challenges in Brazil as well as uncertainty in the UK. However, its geographic diversity, financial strength and low valuation make it a star long term buy.

For example, Santander is a true global banking major. It operates in a wide range of geographies, which should offer some protection against weakness in key markets. And with a P/E ratio of only 8.1, it seems to offer excellent value for money. That's especially the case following its fundraising of 2015, which saw it seek EUR7.5bn from investors in a share sale. Although this may not prevent nervous investors causing volatility in Santander's shares in the short run, it improves the bank's long term prospects and helps to make now a great time to buy it for the long haul.

Wait for further news

Meanwhile, shares in Shawbrook(LSE: SHAW) have fallen by a further 7% today, after the release of a trading update. It contains details of an irregularity in the bank's Asset Finance division which saw a number of loans being underwritten which did not meet the business's strict lending criteria. As a result of this, Shawbrook expects to book an additional impairment charge of £9m, which is clearly disappointing for the bank's investors.

With Shawbrook being UK-focused, its future performance is largely dependent upon how the UK economy -- specifically the housing market -- performs. With uncertainty being high, and the UK housing market already being overheated, it may be prudent to await further news from Shawbrook before buying a slice of it.

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Peter Stephens owns shares of Barclays. The Motley Fool UK has recommended Barclays. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors.