On our plots there are so many voles, mice and rats that direct sown peas = rodents' dinner!
I sow three to a module, in a nine module size half tray, (you coud use paper pots of course) and plant them out as a clump when about four inches tall. I even remove the remains of the pea seed from each stem or otherwise the little varmints snip through the stem to take these away, and that is the end of the plant. Clumps are planted about our inches apart. I realise in Dave's book this equates to "faff" but it is the only way I can get a crop. Sowing is very quick, so is planting out. Not everyone needs to take off seed remains!!!
Depends how many you grow as to whether this is feasible. I have 36 modules of maincrop peas for outside, sown two days ago, 18 of suagr snap, 12 of early peas and 12 of early mangetout. These early ones are already planted in the polytunnel and are just over a foot tall