Trying to build a £1m portfolio with FTSE 100 shares might sound unrealistic — especially with markets wobbling and headlines dominated by geopolitical tension. But that framing misses the bigger picture.

The real challenge isn’t just finding the next winner. Markets move in cycles, sentiment shifts quickly, and even strong shares can go nowhere for long periods.

So if short-term price moves can’t be relied on, what actually drives long-term wealth?

Durable moats

At some point, every business runs into disruption. Markets turn, costs rise, and demand weakens. But not all companies respond in the same way.

The strongest tend to have something others don’t — durable competitive advantages, strong cash generation, and the financial flexibility to keep investing when rivals are forced to pull back.

In fact, periods of uncertainty can strengthen their position. While weaker players retrench, these businesses can take market share, expand their footprint, and emerge from the cycle in a stronger position than before.

The question, then, isn’t what the market does next — but which businesses are positioned to come out of it stronger.

Spoilt for choice

In 2026, a number of FTSE 100 business models have been put to the test.

National Grid has faced scrutiny over a rising debt load, yet it continues to expand its regulated asset base, doubling down on long-term grid investment.

Meanwhile, RELX has had to contend with the rise of generative AI disrupting parts of its legal and information services. But it’s still investing heavily in data, analytics, and platform capabilities.

Aviva: a different kind of insurer emerging

For me, the standout opportunity in the FTSE 100 right now is Aviva (LSE: AV.)  It’s not because the share price has surged. It’s because the business underneath it has changed.

On the surface, it still looks like a large insurer. But the way it’s now competing points to something very different emerging: a more scalable, data-driven financial platform rather than a traditional cycle-dependent underwriter.

That shift has already been tested in practice. Rising claims costs and inflation exposed weaker players across the sector, with Direct Line a clear casualty. By contrast, disciplined underwriting — particularly tighter pricing and risk selection — allowed Aviva not only to navigate the cycle, but to acquire from a position of strength.

Scale now matters less as a growth driver and more as a structural advantage that stabilises earnings through the cycle.

That advantage is reinforced by data and machine learning embedded across pricing and claims, with AI increasingly positioned as a long-term lever for cost efficiency.

At the same time, a larger multi-product customer base reduces churn and improves the predictability of returns.

What’s the verdict?

This is still a transformation in progress, not a finished story. The key risk is execution. If the expected benefits from scale, data, and AI take longer to feed through than management assumes, then delivery of targeted earnings growth over the next three years could fall short. That would likely weaken confidence in margin stability and cash generation, and could weigh on sentiment.

That said, strong businesses often evolve their models while maintaining earnings momentum. Markets do not always price in that shift immediately.

For investors seeking high-quality UK names that may still be underappreciated, this is one to watch closely. The valuation may not yet fully reflect the story.