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Searching for top shares to buy in a Stocks and Shares ISA? Here are a couple from the FTSE 100 and FTSE 250 to consider right now.
Babcock International
A bright outlook for the European defence sector suggests Babcock International (LSE:BAB) could remain one of the FTSE 100’s star performers.
Up 64% over the past 12 months, the business — which provides engineering, support and training services to global armed forces — was promoted to the Footsie in March.
Yet I believe it remains undervalued at today’s price of 833.5p per share. With a price-to-earnings (P/E) ratio of 17.4 times, it remains far cheaper than other heavyweight UK defence shares like BAE Systems (22.2 times), Rolls-Royce (32.2 times) and Chemring (20.6 times).
Its sub-1 price-to-earnings growth (PEG) ratio of 0.3 times also suggests its shares are seriously cheap. This provides scope for more significant share price gains given the pace at which weapons spending is soaring.
Babcock’s capitalising effectively on this fertile landscape thanks to its strong global relationships and expertise in key areas (its tasks include maintaining the UK’s fleet of nuclear submarines, for instance). Revenues rose 11% in the 12 months to February 2026, while operating profit leapt 17%.
On the negative side, persistent supply chain issues in the defence sector could compromise future earnings growth. Yet I think this is more than reflected in its low valuation.
Babcock could be interesting because of its limited exposure to the US. As a consequence of this, profits are less dependent on Stateside defence spending, which could fall dramatically in the coming years.

Hochschild Mining
Silver producer Hochschild Mining (LSE:HOC) has also soared over the last year, in this case driven by increasing precious metals prices. At 278.9p per share, the FTSE 250 company’s up 77% since this point in 2024.
The company mainly produces silver from its mines in The Americas. However, it also produces not-insignificant amounts of gold, allowing it to capitalise on the yellow metal’s surge to repeated highs.
Looking ahead, I think Hochschild could deliver superior share price gains than pure-play gold stocks. This is because of silver’s current cheapness relative to gold, leaving ample room for the grey metal to outperform its precious cousin.
The gold/silver ratio — which measures the value of once silver ounce relative to one of gold — is currently at 1:99, which is high by historical standards. Bullion dealer Sharps Pixley notes that the ratio peaked at 1:128 during the pandemic when gold prices peaked before toppling to 1:70 in the months following.
It says that “with gold at $3,200 per ounce, a 1:70 ratio would put silver at $45.70.” That potentially provides substantial upside from current levels of $32.88 (gold was recently changing hands at $3,247.20).
Of course there’s no guarantee that silver prices will rise. And even if they do, production problems may hamper Hochschild’s ability to exploit this, a constant risk in the mining industry.
But on balance, I think the company’s worth serious consideration from ISA investors, and especially at current prices. It trades on a forward P/E ratio of just 8.4 times, and carries a PEG of 0.1.