Well, I think this Lettuce has not suffered from lack of space:
Actually there are two of them, side by side.
I haven't harvested them yet (waiting for a suitable opportunity to appear on the menu!), but they seem right - in other words the hearts feel firm and heavy, so they should be good.
Adopting the completely opposite approach I have recently planted out loads of tiny Lettuce seedlings, spacing them very closely.
These are ones left over after selecting the best ones for temporary potting-up, awaiting their turn in the Salad Bed. I hadn't the heart to just dump them in the compost, so I thought I would grow them as what I call "Cutting Salad", in other words I will pick their leaves individually while they are still small rather than letting them mature. My second sowing of mixed Cutting Salad has run to seed and been removed now, so these Lettuce seedlings have become available at a very convenient moment.
I have left in place a few of the less bedraggled plants from the recently-removed Cutting Salad, such as one or two Endives. My "deliberately-sown" Endives are not doing well so far (mostly bolted), so I need every Endive I can get. Since we had a fair bit of rain last weekend the soil is nicely damp now, and the Lettuces will grow quickly. I should be able to start taking leaves from them in just a few days from now.