Heathrow is a pair of socks that are knitted cuff down. The only change with the sizes is the stocking stitch panels on the front of the sock.

Sizes - meas circumference at the widest part of the foot.
Sml Med Lge XLge
Ins 8 9 10 11
cms 20.5 23 25.5 28

Materials required
White Gum Merino Wool Sock Yarn - 80% merino and 20% nylon
Yarn required - 1 skein
472m/516y per 100g skein
2.25mm 80cm circular needle
2.50mm 80cm circular needle
1 x cable needle
Pattern is written for magic looping, 2 circulars are
suitable if that is your preferred method
2 stitch markers
Darning needle for sewing in ends

Note 1 - Using a different yarn other than the one suggested may give an unsatisfactory result especially with yardage for the xlge size
Note 2 - Long Tail Cast On
http://www.knittinghelp.com/video/play/long-tail-cast-on

Tension (Gauge)
32 sts and 48 rows to 10cm over stst on 2.50mm needles.

Abbreviations
Appox - approximately, C4B - slip next 2 stitches onto cable needle and hold at back of work, work next 2 stitches off left hand needle, then knit the 2 stitches off the cable needle, C4F - slip next 2 stitches onto cable needle and hold at front of work, work next 2 stitches off left hand needle, then knit the 2 stitches off the cable needle, cm - centimetres, ins - inches, k - knit, k2tog - knit the next 2 stitches together, meas - measures, p - purl, p2tog - purl the next 2 stitches together, pm - place marker, rep - repeat, sl1pw - slip 1 stitch purlwise, sm - slip marker, ssk - slip, slip, knit the 2 slipped stitches together through the back of the loop, st(s) - stitch(es), tw2 - twist 2 by knitting the next 2 stitches together, do not slip off the left hand needle, knit into the first of these stitches again, then slip both stitches off the needle.