The average monthly rent for that year was £759, according to statistics aggregator Statista, covering these monthly repayments. Alternatively, an interest-only mortgage would cost the landlord £503 a month, letting them pocket £256 a month in rental income.

However, today the same property would be worth £270,027: £52,616 more than its original value. 

Investing the same deposit in a medium-risk portfolio returning 4.5pc would have earned just £17,405 over the same time according to insurer Aviva.

This means the buy-to-let investor would be around £35,211 better off, minus maintenance costs and tax, and could benefit further from house price growth in the future.

However, experts have urged caution over relying on one kind of investment for pension income. Insurance firm Prudential warned that the risk involved in investing in a single asset class to fund retirement may have increased over the past five years.

The buy-to-let sector is now far less attractive than it was five years ago due to government changes, which have successively stripped away many of the tax advantages that landlords used to enjoy.

The biggest change landlords have faced in this time has been the tapering and removal of mortgage interest tax relief. 
Landlords could previously deduct mortgage expenses from their rental income to reduce their tax bill. This is no longer the case and landlords instead receive a tax credit based on 20pc of their interest payments.

This means higher-rate taxpayers, who previously effectively received 40pc tax relief on their mortgage payments, now pay more in tax. Under the new system, having to declare income used to pay a mortgage has pushed some landlords into higher or additional tax brackets.

Landlord organisations claim this has forced a quarter of a million to sell up and exit the market over the past five years. 
By comparison, investment returns within a pension are not subject to income tax.

There are other tax implications to consider. Pension investment returns are free from capital gains tax. This is not the case for buy-to-let property, but landlords can deduct purchase and sale costs.

Defined contribution pensions can also be passed down without incurring inheritance tax. But buy-to-let properties form part of a deceased landlord’s estate, and as such are subject to IHT.

Meanwhile, if a pension holder dies before 75, their beneficiaries can access their pot free of income tax, and can access funds at a marginal rate if the holder died after 75. 

This is not the case for income from buy-to-let properties, which is liable to the tax regardless of when the landlord died.