16th September 2026
Blockchain is one of those words that has become part of everyday conversation without many people being quite sure what it actually means.
It is associated with Bitcoin, cryptocurrencies, smart contracts and a whole range of new financial technologies. Supporters describe it as revolutionary. Critics sometimes see it as an unnecessarily complicated way of doing things that banks and other institutions already do perfectly well.
So what exactly is blockchain?
The simplest way to understand it is to imagine a shared record book.
Suppose 1,000 people each have an identical copy of the same book. Whenever somebody makes a transaction, the details are announced to the group. The network checks that the transaction is legitimate and, once agreed, records it in the next available section of the book.
Everybody's copy is then updated.
That is broadly what a blockchain does.
A "block" is a batch of transactions or other information. The blocks are then linked together in chronological order, creating a chain. Hence the name blockchain.
Why not just use a bank?
This is the fundamental question.
If you transfer £100 from your bank account to somebody else's account, you don't need a blockchain.
Your bank has a database recording how much money you have. When you make the transfer, the bank changes the balances in its records.
The bank is the central authority.
Blockchain attempts to remove the need for that central authority.
Instead of one organisation maintaining the definitive record, copies of the ledger can be maintained across a network of computers.
The idea is that the participants don't have to trust one central organisation. They trust the rules of the system and the cryptography that protects it.
But who decides what is a genuine transaction?
This is where the technology becomes more complicated.
A blockchain needs some way of reaching agreement about which transactions are legitimate and which should be rejected.
This is called a consensus mechanism.
Bitcoin uses something called proof of work. Computers compete to solve mathematical problems and the successful participant gets the opportunity to add the next block to the chain, subject to the network's rules.
This requires considerable computing power and electricity.
Other blockchains use different approaches.
Ethereum, for example, uses proof of stake. Participants put cryptocurrency at risk as part of the process of validating transactions. The system's rules determine how validators are selected and what happens if they behave dishonestly.
The important point is that there isn't necessarily a person sitting in an office checking every transaction.
The software, cryptography and network participants collectively perform that function.
Can somebody simply change the records?
This is one of blockchain's main attractions.
Imagine somebody has successfully completed a transaction and it has been incorporated into the blockchain.
They cannot simply alter their own copy of the ledger and expect everybody else to accept it.
The other computers on the network have their own records.
If one copy suddenly says that a transaction was for £1 million while everyone else's says £10, the altered copy does not match the network.
The cryptographic links between blocks also make changing historical information difficult.
That does not mean blockchain systems are invulnerable. Cryptocurrency exchanges, wallets, smart contracts and individual blockchain networks can all be attacked or compromised.
Blockchain technology is not a magic security shield.
Its security comes from the combination of cryptography, distributed records and the particular consensus rules used by the network.
So does anyone control Bitcoin?
This is where things get interesting.
Bitcoin does not have an owner or central authority in the way that a bank does.
There is no Bitcoin chief executive who can announce that the rules have changed.
There are developers who work on the software. There are miners who provide computing power to the network. There are large Bitcoin holders and businesses that provide exchanges, wallets and other services.
All of these groups can have influence.
But influence is not the same as control.
A developer can propose a change to the Bitcoin software, but that does not mean everyone using Bitcoin has to accept it.
The people operating the network ultimately decide which version of the software and which rules they will follow.
This is one reason changes to major blockchains can sometimes be extremely contentious.
Ethereum shows another side of blockchain
Bitcoin is probably the best-known example, but blockchain technology goes considerably further.
Ethereum allows something called smart contracts.
A smart contract is essentially computer code stored on the blockchain that can carry out instructions automatically.
Imagine a simple agreement saying that if condition A occurs, £100 should be transferred to person B.
Instead of relying on a bank employee or other intermediary to execute the agreement, the software can do it automatically when the specified conditions are met.
That is the attraction.
It is also the risk.
If the code contains a mistake, the system may execute the mistake just as efficiently as it would execute the intended transaction.
Not every blockchain is decentralised
This is an important point that is often missed.
When people say "blockchain is decentralised", they are really talking about particular types of blockchain.
A public blockchain such as Bitcoin is designed to operate without a central controlling organisation.
But a company can also create a private blockchain.
It might restrict who can participate, decide who can validate transactions and retain considerable control over the system.
A group of banks could, for example, create a blockchain-based system for transferring information between themselves.
There would still be a blockchain, but it would not operate in the same way as Bitcoin.
So the word blockchain by itself tells us very little about how much control exists.
What about governments?
Governments generally cannot simply reach into Bitcoin's blockchain and delete a transaction.
But they can regulate the businesses surrounding it.
An exchange operating in Britain, for example, can be subject to financial regulations. Governments can also impose taxation requirements and regulate banks dealing with cryptocurrency businesses.
This creates an interesting distinction.
A government may not control the Bitcoin network itself, but it can have considerable influence over the points where ordinary people interact with cryptocurrency.
There is a price for decentralisation
Blockchain's supporters often emphasise the fact that there is no central authority.
But that feature also creates problems.
Suppose somebody transfers cryptocurrency to the wrong address.
With a traditional bank, there may be somebody to contact. The bank can investigate the transaction and, in some circumstances, attempt to recover the money.
With a genuinely decentralised blockchain, there may be nobody with the authority to reverse the transaction.
If you lose the private key that gives you access to your cryptocurrency, there may be no bank manager who can prove that you are the rightful owner and reset your access.
You are responsible for your own security.
That is both the attraction and the danger.
Is blockchain really revolutionary?
That depends on what problem you are trying to solve.
If the job is simply transferring pounds from one British bank account to another, a blockchain may add complexity without providing an obvious advantage.
The existing banking system already maintains a centralised ledger and has sophisticated systems for checking transactions, dealing with fraud and resolving disputes.
Blockchain becomes more interesting when several parties need to share a record but do not want to rely entirely on one organisation to maintain it.
That could have applications in areas such as international finance, supply chains, digital ownership and automated contracts.
Whether all those potential applications will prove worthwhile is another matter.
The simplest way to remember it
Think of a conventional bank as having one trusted record keeper.
Blockchain replaces that model with a network of participants following agreed computer rules and maintaining a shared record.
The important question is therefore not simply:
"Is blockchain decentralised?"
The better question is:
"Who has the power to change the rules, validate transactions and resolve disputes on this particular blockchain?"
For Bitcoin, that power is deliberately spread across the network.
For a private blockchain operated by a company, it may be concentrated in the hands of the organisation running it.
And that is perhaps the most important thing to understand about blockchain.
It is not really about a magical new type of money.
It is about how a group of people can maintain a common record without necessarily having to trust a single organisation to control it.
Whether that is better than having a trusted organisation in the middle depends very much on what the system is being used for.