It is the ninth and final round of the HSBC Sevens World Series where Gareth Williams’ side currently sit in 10-equal place overall.
Walsh and Field replace Iolo Evans and Gareth Owen in a side which faces series leaders New Zealand, England and Argentina in their pool.
This weekend will be Field’s first appearance in the series since the second round in Dubai while Walsh will be making his debut.
Wales will be looking to bounce back from last weekend’s tournament in Glasgow where they claimed the Shield final after finishing bottom of their pool with defeats to Argentina and Fiji after starting their campaign with a win against Kenya.
Wales Sevens squad for Marriott London Sevens
Adam Thomas (Pontypridd – Capt)
Rhys Shellard (Pontypridd)
Sam Cross (Cardiff Met)
Jason Harris (Carmarthen Quins)
Lee Williams (Carmarthen Quins)
Ross Jones (Bridgend)
Will Thomas (Cardiff)
Will Price (Aberavon)
Geraint Walsh (Pontypridd)
Owen Jenkins (Pontypridd)
Adam Field (Bridgend)
Luke Morgan (Bridgend)
