Broadchurch: What is inside Lucas's secret drawer?

Viewers were afforded the swiftest of glimpses so we've taken it upon ourselves to do some in-depth analysis:

Trish (or Leah's?) keys

The most obvious article in Lucas's drawer is a bunch of keys with a keyring picturing Trish and her Leah. Do they belong to Trish? Or her daughter? Why are they in Lucas's possession – and does he plan to take advantage of his access to their house?

Of his collection, it's this that piques his interest – he picks up the keys and examines them – but they're already in the drawer when he opens it which suggests he acquired them a little while ago, perhaps on the night Trish was attacked?

The new addition

The keys to Trish and Leah's house aren't the only set in Lucas's possession. As he unlocks his sinister cabinet, he digs out a new bunch and adds them to the rest of his objects. But who do they belong to? The image on the keyring is too grainy to make out properly...

... and could belong to any number of Broadchurch residents. Neither woman looks much like Cath Atwood, but could they be the property of Ellie Miller, Beth Latimer or Daisy Hardy? None have had much to do with Lucas (that we know of).

Which leads us onto the question, what does Lucas's collection actually represent? Are these trophies taken from his victims – and, if so, has he been attacking women for years and stealing mementos?

Or – and we're attempting to give him the benefit of the doubt here – are they reminders of the women he's cheated on his wife with? She alluded earlier in the episode to his frequent infidelities – does each represent a different dalliance? That would cover the inclusion of Trish's keys, given that the pair went for a drink and Lucas clearly harbours some feelings.

The rest of the drawer...

Lucas's stash is brimming with miscellaneous items, many of which appear to be feminine. The sunglasses, third keyring and shiny phone probably belong to a woman, although the wallet and King of Spades are harder to explain.

What is clear is that all these items would be missed by their owner. On the other side of the drawer is a second phone and a wristwatch. Whatever the reason behind Lucas's theft, it's clear he wants the possessors to notice what's missing.

That is, unless most of the owners are no longer around to realise they're gone...