Over the past 18 months, hundreds of people have travelled from the UK to fight in Syria. Most have joined the self-styled Islamic State. Could banks assist the security authorities identify some of these so-called foreign fighters by uncovering "telltale" financial footprints?
Banks create immense troves of data as they process transfers, ATM withdrawals, and credit card transactions.
Consider the way a credit card issuer calls to enquire whether the recent user of your card in an uncharacteristic location was indeed you. Or the uncanny ability that large retailers have of predicting what you might want to purchase next.
All this is achieved via the monitoring of financial activity based on the extensive transaction experience that banks and other financial service providers have developed.
Syria's conflict is the most socially mediated civil conflict in history, with endless tweets, and Facebook and Instagram postings promoting the jihadi cause.
Online channels are also used to offer financial and travel advice to those aspiring to join the fight, answering enquiries about hotels, border crossings, how much money to bring, services provided by Islamic State, visa requirements, and even whether wi-fi and contact lenses are available.
One fighter reportedly advised those travelling to make sure they have enough money to cover staying in Turkey in case transit to Syria is delayed and to avoid raising suspicion in airports by carrying no more than £3,000 (suggesting that if challenged, travellers should simply say they are taking an "extravagant holiday").
Information is also said to be provided for those wondering how much money they will need for living expenses: "Not much several hundred, u dnt need much, u get wages here, u get food provided and place to stay," says one fighter, while another reportedly agrees: "Nothing really at all - [all] is provided. All that's needed is to pay towards getting here."
Others provide answers to more specific financial questions such as to whether weapons or clothing have to be paid for. "No" is the response, "we get weapons from Dawlatul-Islamiyyah [referring to Islamic State]".
But if a fighter wants to buy a specific weapon he is advised that a modern AKM Kalashnikov assault rifle costs US$1,200 (£760), while older AK-47s cost even more.
Likewise, clothing is provided by Islamic State but can also be bought and even tailored for the aspiring jihadi. And it is not just the social media activity of these individuals that provides insight into their motives but also their financial transactions.
On their own, the purchase of airline tickets and camping/outdoor gear and the withdrawal of an unusually large amount of cash from a bank account are hardly grounds for suspicion.
But when combined with account activity that indicates the accountholder has used ATMs in known jihadi-gathering locations, has taken a consumer loan that is in arrears or in default, has received an unusual number of typically small payments that might be from supporters or donors, or has received a student loan but is not attending classes, a different picture begins to emerge.
While it would be naive to suggest that banks have the ability to produce a form of financial "minority report", the amount of data they can access in tackling fraud and other financial crime is immense.
Both banks and law enforcement recognise the potential value in working more closely together and, within the limits of data privacy laws, sharing intelligence that can improve the quality and effectiveness of the information banks can provide to police and security agencies.
The government has recently announced efforts to enhance this partnership, but engagement between the authorities and banks in exploiting this capability for security purposes remains limited despite the obvious benefits it can bring.
At a time when many judge that "British citizens who have joined terrorist groups in Syria and Iraq pose a threat to the UK" and the United Nations is calling for "increased sharing of information for the purpose of identifying foreign terrorist fighters", to ignore the banking sector as a partner in combating this threat seems at best a curious oversight and at worst a national security weakness.
Tom Keatinge is Director of the Centre for Financial Crime and Security Studies at the Royal United Services Institute (RUSI).