Aspleniums (Hart's Tongue fern) and blechnum spicant are two ferns that will thrive in dry shade. Sarcococca (Christmas Box) with scented flowers in February and epimediums, which also flower in spring, will also relish the condtions

Make leafmould from fallen leaves, and mulch the bed with it, as that would help retain moisture. It does take a year or more to rot down, though - in black binbags or a wire enclosure.

In the mean time, add homemade compost, water well, and then mulch over the bed with slate chippings or something else to keep the moisture in.

My concern is that I think I can see a Rosemary bush at this end of the bed - that wouldn't like a damp area.

Although the walls in your pic suggest at least some shade for this area the walls also shelter the ground from rain, the rosemary in the foreground seems to be doing well and this likes dry sunny sites.I think most ferns could do well here (as is the one in the photo)as long as the soil is prepared and plants well watered for the first year.

The most ideal spot in the picture is the corner where the two garden walls meet, this is a dead end for water drainage and it will collect there if it is at the end of a slight downward grade. For added moisture insurance dig a hole of a diameter of your choice and of a depth of at least 16 inches-a bit deeper if you can. Then line the bottom and sides with one layer of slightly overlapping 30gal size plastic kitchen garbage bags. Fill in the bottom 1/2 of the lined hole with good potting soil and top off with well composted manure. Set in the fern and add a good layer of pine mulch or pine needles. Water well. The plastic liner will keep the soil most around the fern but not under bog like conditions. Water every other day with one gallon of water from a watering can not a garden hose. This way you will soon learn the best amount of water to use to keep the fern's environs moist. The slight overlap of the plastic bags will allow for slow drainage.

Thanks all for the ideas,I like you idea Graterford as wHere this area is there is only about 10'' topsoil so I always have to dig out a foot of clay before I plant anything anyway.Thanks also for the tips from spritxhenry and and Dgw, what the picture does not show is that to the right of the path, is the house wall, so you can appreciate why I thought of putting ferns in. it only gets a couple of hours of sun in midsummer.The rosemary does do well there, Ihave to keep trimming it back. The ferns i am thiking of putting in would be behind the existing fern and not by the rosemary.thanks for your suggestions Henryr I shall have a look at them