WATCH: Scotland fans descend on London full of belief ahead of England clash

The Tartan Army have invaded London full of belief ahead of the World Cup qualifier against England:

> VIDEO REPORT: Atmosphere building in London ahead of the big game. pic.twitter.com/8oP7W7xn51> > > — Superscoreboard (@ClydeSSB) November 11, 2016

Scotland take on England at Wembley looking to get their 2018 World Cup qualification campaign back on track.

Here, we focus on the key issues which may have an impact on the result for Gordon Strachan's side.

FORM

Scotland's long-term and short-term form is poor. The Scots have not qualified for the finals of a major tournament since the 1998 World Cup in France and Russia in 2018 is already looking a forlorn hope. A win away to Malta in their Group F opener was no more than expected but a 1-1 home draw with Lithuania and a 3-0 defeat in Slovakia last month left the Tartan Army despondent. Scotland need a big turnaround in fortune starting against the Auld Enemy.

TACTICS

Strachan normally plays a 4-2-3-1 and is unlikely to change for Wembley. The two sitting midfielders - Scott Brown is set to be one after his return from his short retirement - shield a central defence which often creaks. The lone striker's role is key with Steven Fletcher and Chris Martin ahead of Leigh Griffiths in the pecking order but the former two are not prolific while the Celtic striker suffers from the lack of opportunity.

DEFENCE

The weak link of the Scottish side. Grant Hanley and Russell Martin have come in for constant criticism in recent years but there are not a lot of options available to Strachan. Injuries to left-backs Andy Robertson and Kieran Tierney have left that positioned weakened while right-back Alan Hutton only recently declared himself retired. Callum Paterson will again start at the right of the back-four with Rangers skipper Lee Wallace likely to come in on the opposite flank. It will be another tough test for the visitors.

KEY PLAYERS

It is likely that keeper David Marshall will have to be on top form if Scotland are to get a result but the Hull City number one is normally steady. Midfielder Brown will have to energise the midfield and set a high tempo for the visitors who will need to play with an intensity and desire which will unsettle the Three Lions.